Recent methods for the diagnosis and differentiation of ameloblastoma: a narrative review

Abstract

Ameloblastoma is a benign but locally invasive tumour. Early diagnosis of ameloblastoma and formulating an appropriate treatment plan play a crucial role in reducing the postoperative recurrence rate. The imaging features of ameloblastoma are similar to those of other odontogenic diseases; thus, the diagnosis of ameloblastoma remains challenging. This review summarises the diagnostic techniques used for the detection of ameloblastoma and the methods for differentiating it from other benign odontogenic tumours to aid in the clinical diagnosis. A comprehensive review was conducted by searching the database of PubMed for studies published up to May 2023. Panoramic radiography, computed tomography, and magnetic resonance imaging have been used to detect ameloblastoma, whereas fine-needle aspiration cytology and biopsies have been used to enhance diagnostic precision and clinical diagnosis. ¹⁸F-fluorodeoxyglucose (FDG) and FDG positron emission tomography(PET) have been used to detect metastasis of ameloblastoma to determine the prognosis of the disease. Laboratory tests are more suitable for detecting genetic alterations and identifying certain markers. Different diagnostic techniques aid in differentiating ameloblastoma from other odontogenic diseases. Combining these techniques may increase the diagnostic accuracy in patients with suspected ameloblastoma.

Key policy highlights

• This review summarises the methods for diagnosing ameloblastoma. This is the first comprehensive review of the procedures used for diagnosing ameloblastoma.

• The benefits and limitations of several diagnostic techniques were examined in this review.

• Cone-beam computed tomography is the most appropriate radiological technique for the detection of ameloblastoma. ¹⁸F-FDG PET/CT showed high diagnostic accuracy in identifying metastatic/recurrent lesions postoperatively.

• The detection of cytokines and gelatinase in the cyst fluid further aids in the diagnosis.

• The techniques discussed in this article aid in the diagnosis of various types of ameloblastoma, which will increase diagnostic precision.

Keywords:

• Ameloblastoma
• technology, radiologic
• biopsy, fine-needle
• biopsy, incision
• positron emission tomography
• computed tomography

Introduction

Ameloblastoma is defined as a slow-growing benign but locally aggressive odontogenic lesion that frequently develops in the mandible. Ameloblastoma typically manifests as a painless swelling on the outer margins of the cheeks and lips. Oppressive growth of the lesion can result in dysfunction and facial dysmorphisms. Expansion of ameloblastoma developing in the mandible results in the compression and thinning of the bone as well as mobility or loss of teeth in the vicinity of the tumour.

Ameloblastoma is the most prevalent odontogenic tumour in developing countries, and it is observed more frequently in individuals between the ages of 30 and 60 years. The discovery of mutations in the BRAF V600E and SMO genes in patients with ameloblastoma in the last decade has provided insights into the pathophysiology of this disease (Ghai 2022). Although ameloblastoma is a benign tumour, it has a malignant transformation rate of 70%. The rate of metastasis is higher in the mandible than that in the maxilla, and the lungs and lymph nodes are the most frequent secondary sites (Effiom et al. 2018; Ghai 2022).

Surgery, including both conservative and aggressive measures, remains the treatment of choice for ameloblastoma. Although conservative treatment results in fewer facial abnormalities, the recurrence rate is higher than that of aggressive therapy. Consequently, the treatment and prognosis of ameloblastoma are determined based on the clinical and histological results.

The diagnosis of ameloblastoma is the first step in the treatment of ameloblastoma (Effiom et al. 2018). Arriving at the correct diagnosis and formulating an appropriate treatment plan are the key to reducing the postoperative recurrence rate. Benign odontogenic lesions, such as ameloblastoma, odontogenic keratocysts, and dentigerous cysts, are the most prevalent odontogenic lesions encountered in clinical practice. Although these lesions are odontogenic, significant biological and treatment differences have been observed among them. Different treatment approaches have been developed owing to the differences in the recurrence rates. Thus, the accurate diagnosis and identification of ameloblastoma is crucial (Liu et al. 2021; Wamasing et al. 2022).

This review aims to summarise and analyse the methods for diagnosing ameloblastoma and the methods for differentiating ameloblastoma from other benign odontogenic lesions to aid in the clinical diagnosis of ameloblastoma, reduce the recurrence and metastasis of ameloblastoma, and improve the diagnostic accuracy.

Materials and methods

Search strategy

The PubMed database was searched to retrieve articles published between 1965 and May 2023 on the diagnosis of ameloblastoma and the identification of ameloblastoma and other odontogenic diseases. The following terms were used to search the database: ‘ameloblastoma’ and ‘diagnosis’ or ‘diagnostic imaging.’ Only studies published in English or Chinese language were included in this review.

Study selection

All retrieved articles were reviewed to ensure that the inclusion and exclusion criteria were met.

The inclusion criteria used in this review were as follows: (1) studies published after 2017 and their studies on conventional ameloblastoma, unicystic ameloblastoma, extraosseous/peripheral ameloblastoma, and metastatic (malignant) ameloblastoma were included in accordance with the ameloblastoma classification criteria put forward in 2017; (2) articles published before 2017 were re-evaluated by combining the four versions of the classification criteria and were included if they still belonged to the classification put forward in 2017; (3) studies that also discussed diagnostic predictors of ameloblastoma and differences between ameloblastoma and other odontogenic disorders; (4) studies that used various diagnostic techniques for diagnosing ameloblastoma; and (5) studies that evaluated the benefits of various diagnostic techniques.

The exclusion criteria were as follows: (1) reports of simple clinical cases without a diagnosis; (2) articles published before 2017 that were still not part of the classification criteria put forward in 2017 after re-evaluation were excluded.

Seventy articles were included in this review. All articles that met the inclusion criteria were processed for information extraction. Data regarding the year of publication, authors, contents, and the main results were extracted. Tables 1 and 2 present the details regarding the articles and primary findings of the studies.

Table 1. Suitable diagnostic technique for clinical diagnosis.

Study	Year	Study contents	Study results
Cardoso LB et al.	2020	Panoramic Radiography (PR) and Cone Beam Computed Tomography (CBCT)	CBCT images revealed that the size and degree of expansion of ameloblastoma are larger than those of odontogenic keratocysts and dentigerous cyst.
Wamasing N et al.	2022	Conventional Magnetic Resonance Imaging (MRI) and diffusion-weighted imaging (DWI)	The apparent diffusion coefficient (ADC) helped distinguish unicystic ameloblastoma from dentigerous cyst and odontogenic keratocysts; however, it cannot be used to distinguish dentigerous cyst from odontogenic keratocyst.
Alves DBM et al.	2018	PR and Computed Tomography (CT)	Although PR is very useful and widely used, CT provides more accurate information on buccolingual expansion, calcification, bone septa, perforation of cortical bones, and tooth resorption.
Apajalahti S et al.	2015	CT and MRI	Enhanced CT and MRI can help distinguish between ameloblastoma and other cyst-like lesions as they enable the visualisation of the mixed cystic and solid content characteristic of non-unicystic ameloblastoma. CT and MRI aid in determining the differential diagnosis of unicystic ameloblastoma.
Wakoh M et al.	2011	PR	The degree of observer reliance on diagnostic elements is more consistent for ameloblastoma than for odontogenic keratocysts in PR. In particular, ‘radicular state adjacent to a lesion' may be a decisive factor for distinguishing ameloblastoma from odontogenic keratocyst.
Cihangiroglu M et al.	2002	CT and MRI	Both CT and MRI show the extent of the tumours.
Crusoe-Rebello I et al.	2009	CT	CT parameters facilitate the evaluation of ameloblastoma and odontogenic keratocysts as well as other lesions.
Shokri A et al.	2017	CBCT	CBCT can clearly visualise the borders and internal structures, cortical expansion, and effect of lesion on adjacent tissues; thus, its use is recommended.
Li D et al.	2018	CBCT	The rotated three-dimensional CBCT images clearly display the exact size, location, and borders of the tumour, as well as the internal changes in the tumour in the jaw cyst and the adjacent tissues. Therefore, CBCT aids clinicians in evaluating lesions and developing better treatment plans.
Surenthar M et al.	2021	CBCT	CBCT plays a crucial role in addressing the diagnostic challenges faced and separating it from other cystic lesions.
Luo J et al.	2014	CBCT	CBCT can provide more information for preoperative radiologic assessment of desmoplastic ameloblastoma compared with PR.
Meng Y et al.	2018	Spiral CT and CBCT	Ameloblastoma, odontogenic keratocyst, and dentigerous cyst are common benign lesions of the maxilla, and the three-dimensional imaging information provided by spiral CT and CBCT facilitates their diagnosis and differential diagnosis.
Saati S et al.	2017	CBCT	CBCT may be beneficial for dentomaxillofacial imaging considering the low radiation dose and high resolution.
Kawai T et al.	1998	CT and MRI	MRI is the optimal method for displaying tumours. MRI is crucial for determining the exact degree of advanced maxillary ameloblastoma.
Heffez L et al.	1988	MRI	MRI is superior to CT in evaluating recurrent diseases as it can distinguish tissues based on their proton composition
Cassetta M et al.	2014	MRI	The acquisition sequence enables us to emphasise the diagnostic efficacy of MRI in characterising the morphology and structure of maxillofacial lesions, and demonstrates the importance of this imaging method as an additional technique to CT in maxillofacial surgery planning, thereby reducing the risk of injury to the inferior alveolar nerve during surgery.
Gupta A et al.	2018	Fine – needle Aspiration Cytology (FNAC)	FNAC is a simple, rapid, accurate, inexpensive, and minimally invasive procedure for the diagnosis of ameloblastoma.
Günhan O et al.	1989	FNAC	A case of ameloblastoma diagnosed preoperatively as ‘benign tumoural lesion, suggestive of ameloblastoma' using FNAC has been presented.
Uçok O et al.	2005	FNAC	FNAC is used more commonly for the diagnosis of intraosseous and soft tissue lesions in the oral and maxillofacial regions to obtain sufficient material. It is convenient, inexpensive, and non-invasive.
Perić M et al.	2012	FNAC	Adequate sampling patterns and correct cytological and histopathological diagnosis are important factors for FNAC.
Thambi R et al.	2012	^Cytological	Ameloblastoma provides a good cell yield on aspiration and has distinct cytological features. It is almost as effective as histopathology in appropriate clinical and radiological setting.
Desai KM et al.	2023	FNAC	Careful evaluation of FNAC helps diagnose ameloblastoma and must be considered a vital diagnostic tool.
Reid-Nicholson M et al.	2009	FNAC	Although cytological examination is helpful in diagnosing ameloblastoma, it is not helpful in distinguishing conventional ameloblastoma from malignant ameloblastoma. sufficient sampling is necessary to distinguish conventional ameloblastoma from malignant ameloblastoma.
Hallikeri K et al.	2021	FNAC	Compared with FNAC, cell block technology better preserves the structural patterns and morphology of cells.
Zaidi A et al.	2021	FNAC	The cell blocks created from the aspirate can serve as small biopsies that facilitate accurate diagnosis of mandibular ameloblastoma. Moreover, they contribute to the appropriate treatment of the tumour.
Renapurkar SK et al.	2022	Incisional Biopsies	The findings of incision biopsy is not always consistent with the final diagnosis. The possibility of sampling errors should be considered during biopsy.
Chen S et al.	2016	Incisional Biopsy	The diagnosis of incisional oral biopsy was consistent with the final pathological results in 88.9% of cases. Multiple-site biopsy and larger volume samples facilitate more accurate diagnosis.
Perry KS et al.	2015	Incisional Biopsy	Incisional biopsy is an important first step.
Gliddon MJ et al.	2005	Incisional Biopsy and Endoscopy	Endoscopy may prove to be an important tool. This would especially be the case for large cysts that extend into areas that are difficult to inspect and sample through a standard ‘bony window' technique.
Hai HK et al.	1988	Incisional Biopsy	Regression of large ameloblastoma has been observed after performing a biopsy.
Lin Y et al.	2014	Incisional Biopsy and CT	CT-guided percutaneous transthoracic lung biopsy and lymph node biopsy are important methods for confirming metastatic ameloblastoma.
Fahradyan A et al.	2019	Incisional Biopsy	If the biopsy site of ameloblastic carcinoma is not removed from the malignant site, there will be a lack of evidence supporting the presence of a malignant tumour, leading to a lack of diagnosis.
Otsuru M et al.	2008	^18F-Fluorodeoxyglucose Positron Emission Tomography(^18F-FDG PET/CT)	GLUT-1 expression and FDG uptake may serve as indicators of the proliferation and recurrence of ameloblastoma
Nguyen BD et al.	2005	^18F-FDG PET/CT	^18F-FDG PET/CT aided in the early detection of asymptomatic thoracic spine dissemination, which was not conspicuous on CT examination
Niu N et al.	2013	^18F-FDG PET/CT	^18F-FDG PET/CT is an excellent tool for assessing different malignant processes. Multiple organ metastases from ameloblastoma can be detected using ^18F-FDG PET/CT

Table 2. Advanced imaging techniques and molecular techniques suitable for experimental use.

Study	Year	Study contents	Study results
Poedjiastoeti W et al.	2018	Convolutional Neural Network (CNN)	CNN can be used to distinguish ameloblastoma from odontogenic keratocyst. Its accuracy is comparable with that of manual diagnosis of oral and maxillofacial surgeons. CNN can screen for ameloblastoma and odontogenic keratocysts in a shorter period of time.
Yang H et al.	2020	CNN	Automatic detection convolution network aids in pathological detection and incidence rate prevention in the field of oral and maxillofacial surgery.
Kwon O et al.	2020	CNN	CNN can automatically diagnose odontogenic cysts and tumours of both jaws on PR using data augmentation with high sensitivity
Ariji Y et al.	2019	CNN	Radiolucent lesions of the mandible can be detected with high sensitivity using deep learning.
Lee A et al.	2021	Deep learning neural networks	The present algorithm is expected to be a useful tool for clinicians, as it can be used to diagnose Stafne bone cavity in PR to prevent unnecessary examinations for patients.
Liu Z et al.	2021	CNN	This algorithm improves the diagnostic accuracy of ameloblastoma and odontogenic keratocyst, thereby providing reliable recommendations before surgery.
Vanagundi R et al.	2020	Diffusion-weighted MRI	Addition of diffusion-weighted sequences to MRI jaw protocols can assist in the characterisation of odontogenic keratocyst, unicystic ameloblastoma, and dentigerous cyst.
Oda M et al.	2019	Texture Analysis	CT texture analysis can be used as a non-invasive method to obtain additional quantitative information to differentiate cystic and cystic-appearing odontogenic lesions of the jaw.
Chai ZK et al.	2021	CNN	CNN may provide assistance for clinical diagnosis, especially for inexperienced surgeons.
Yuan XP et al.	2008	Spiral CT	Multi-layer spiral CT can clarify the scope of jaw tumour and changes in the bone. It aids in the qualitative diagnosis and differential diagnosis of diseases. Moreover, it aids in the selection of appropriate treatment options.
Hayashi K et al.	2002	Dynamic Multi-slice Helical CT	Dynamic multi-slice Helical CT distinguishes ameloblastoma and odontogenic keratocyst based on the contrast enhancement values of intra-tumoural vascularities during the arterial phase.
Hisatomi M et al.	2011	Dynamic contrast-enhanced MRI (DCE-MRI)	CE-T1WI and DCE-MRI were helpful in the differential diagnosis of unilocular cystic-type ameloblastoma with homogeneously bright high signal intensity on T2WI or STIR
Hisatomi M et al.	2006	MRI and DCE-MRI	They retrospectively evaluated MRI and DCE-MRI of ameloblastoma.
Sumi M et al.	2008	Diffusion-Weighted MRI	ADC values can be used as an adjunct tool for differentiating ameloblastoma from odontogenic keratocysts.
Han Y et al.	2018	Diffusion-Weighted MRI	Diffusion weighted imaging (DWI) and ADC determination can be used as a tool to differentiate unicystic ameloblastoma from odontogenic keratocyst.
Asaumi J et al.	2005	Contrast-Enhanced MRI(CE-MRI)	CE-MRI is considered useful for diagnosing unicystic ameloblastoma, as only CE-MRI can detect thick enhancement of the tumour wall and small intraluminal nodules.
Gomes JPP et al.	2022	Texture Analysis	MRI texture analysis has the potential to differentiate ameloblastoma from odontogenic keratocyst. MRI texture analysis can be an additional tool to differentiate ameloblastoma from odontogenic keratocyst.
Sant'Ana MSP et al.	2021	BRAF p.V600E	BRAF V600E may aid in establishing the correct diagnosis in cases that microscopically resembling other odontogenic lesions
Pereira NB et al.	2016	BRAFV600E	BRAFV600E may aid in the differential diagnosis of unicystic ameloblastoma with dentigerous and radicular cyst, in conjunction with clinical, radiologic, and histopathological features.
Mendez LD et al.	2022	BRAF VE1	BRAF VE1 is an excellent tool for the diagnosis of mandibular ameloblastoma but of limited utility in the maxilla, where BRAF VE1 and BRAFV600E mutation occur less commonly
Duarte-Andrade FF	2019	BRAF V600E	BRAF-V600E may contribute to metabolic alterations in ameloblastoma. Metabolic alterations might play a role in tumour pathogenesis.
Joshi J et al.	2015	Immunohistochemical markers	Immunohistochemical markers play a very vital role in diagnosingcases
Coleman H et al.	2001	Calretinin	Calretinin appears to be a specific immuno-histochemical marker for neoplastic ameloblastic epithelium and it may be an important diagnostic aid in the differential diagnosis of cystic odontogenic lesions and ameloblastoma.
Kubota Y et al.	2001	Cytokine levels and gelatinase species of the intracystic fluids	Ameloblastoma can be aid in distinguishing it from odontogenic keratocysts by measuring the IL-1a and IL-6 levels, as well as the gelatinase species, in the fluids.
Lu L et al.	2009	Ultrasonography	Ultrasonography can be an effective auxiliary diagnostic method for mandibular ameloblastoma.
Shinohara EH et al.	2013	Ultrasonography	Ultrasonography is the preferred diagnostic tool for evaluating soft tissue lesions in the head and neck region
Beier M et al.	2020	Tomoelastography	Stiffness and fluidity measured by tomoelastography can sensitively detect the presence and extent of bone tumours and metastatic spread to cervical lymph nodes.
Delarue M et al.	2021	Medical infrared thermography (MIT)	MIT can monitor whether there is any diseased tissue passing through the resection edge at the end of the surgery to minimize the risk of recurrence.

Results

Odontogenic keratocysts and dentigerous cysts were frequently distinguished from ameloblastoma in the 70 studies included in this review. Techniques such as fine-needle aspiration cytology, biopsy, the detection of genetic alterations, and the identification of certain markers aided in the diagnosis of ameloblastoma. Imaging techniques, such as panoramic radiography (PR), computed tomography (CT), and magnetic resonance imaging (MRI), have been used for the detection of ameloblastoma. The diagnostic precision of these imaging techniques would benefit from the application of convolutional neural networks and texture analysis. The metastasis of ameloblastoma has been detected using ¹⁸F-fluorodeoxyglucose (FDG) and FDG positron emission tomography (PET) to determine the prognosis of the disease. In addition, tomoelastography, medical infrared thermography, and ultrasonic imaging have also been used to diagnose and treat ameloblastoma. These diagnostic techniques, which aid in the identification of ameloblastoma in clinical settings, have been discussed in further detail below. Table 3 lists the benefits and limitations of these strategies.

Table 3. Advantages and disadvantages of various methods.

	Advantage	Disadvantage
Panoramic Radiography	Simple technique	Two-dimensional imaging
	Lower radiation dosage	Overlap of structures
	Wide inspection scope
	Low cost
Conventional computed tomography (CT)	Three-dimensional imaging	High cost
	Clearer anatomical structure	High radiation dose
	Provide more information	Technique is more difficult than panoramic radiography
		Poor resolution of soft tissue
Cone Beam Computed Tomography (CBCT)	Three-dimensional imaging	Cost and radiation dose are higher than those of panoramic radiography
	Higher spatial resolution.	Poor resolution of soft tissue
	Cost and radiation are lower than those of traditional computed tomography.
	Presents the boundaries, internal structure, and relationship with surrounding structures of the tumour
Spiral CT	Three-dimensional imaging	Low resolution in dental lesions
	Display lesions from multiple directions, such as cross-section	High cost and radiation dose
	High accuracy	The quality of multi-slice spiral CT for fine structures is lower than that of cone beam computed tomography
Conventional magnetic resonance imaging (MRI)	High soft-tissue resolution	High radiation and high cost
	Displays the internal and wall components of the solid cavity
	More suitable for recurrent tumours.
	Effectively images the soft tissue around the lesion, especially distinguishing the surrounding nerves
Diffusion-weighted MRI	ADC values provide valuable information for the differentiation of ameloblastoma
Dynamic contrast-enhanced MRI	Provide diagnostic features for single cyst ameloblastoma (Thick enhancement, intramural nodules)
Fine needle Aspiration Cytology (FNAC)	Simple, fast, safe, minimally invasive, and cost-effective	The sample size is small and sufficient material must be aspirated
	Patient comfort level is good	Requires the assistance of cytologists
	No special equipment required	The sensitivity and specificity of its diagnosis depend on the type of facility and the experience of the cytologists
	Safe for pregnant women, children, and other at-risk patients
Gene mutation	BRAF V600E mutation has certain specificity and frequency, and can be used as a supplementary diagnosis	BRAF V600E mutations are not detected in all patients with ameloblastoma, and this method requires laboratory personnel and special equipment
Biopsy	Appropriate organizational size and depth provide valuable information, which could aid in improving diagnostic consistency	Reliant on the professionalism of pathologists
		Sampling errors, insufficient tissue removal, and the presence of inflammation can affect diagnosis
Ultrasonography	Economical, non-invasive, easy to use, and provides real-time images	If the tumour is small or the cortical bone is not damaged, ultrasound cannot penetrate the bone tissue and can only detect the appearance of the bone tissue
	Can be used without contrast agents and is not subject to ionizing radiation
	Can also provide blood flow information to distinguish between cystic and solid lesions	Large tumours cannot be evaluated
^18F-Fluorodeoxyglucose Positron Emission Tomography (^18F-FDG PET/CT)	Can identify recurrence and metastasis of ameloblastoma
Tomoelastography	Can detect the presence, range, and neck lymph node metastasis of bone tumours, owing to its excellent mechanical parameters (stiffness and fluidity)
Medical Infrared Thermography	Non-invasive, non-ionising, real-time imaging, thermal imaging
	Effectively demonstrates the extension of lesions in soft tissue
Convolutional Neural Network	As a feature extractor, especially for two-dimensional images, it greatly improves diagnostic accuracy
Texture Analysis	Can be applied to computer tomography and magnetic resonance imaging
	As it is based on different texture features, it can differentiate lesions non-invasively and accelerate biopsy and treatment.
Markers	Can identify the levels of cytokines and gelatinase types in the cyst-fluid or the calretinin

Discussion

Clinical diagnostic methods

Panoramic radiography

A radiological examination provides important information to the clinician and aids in the clinical assessment; thus, radiological examinations play an important part in determining the differential diagnosis of ameloblastoma (Cardoso et al. 2020). PR is the most frequently performed radiological evaluation. PR has been used to determine the site of the lesion and sclerosis, in addition to visualising teeth that have not erupted completely. Furthermore, it has enabled the magnification of the lower edge of the cortical bone of the mandible (Alves et al. 2018). PR has numerous variables that may affect diagnostic accuracy, including the image quality of the radiograph and the clinicians’ understanding of the radiological characteristics of the tumour. A higher image quality results in better diagnostic accuracy. Similarly, the clinicians’ understanding of the radiological characteristics of the tumour also affects the accuracy of the diagnosis (Alves et al. 2018; Cardoso et al. 2020).

PR can only yield two-dimensional images; thus, the identification of ameloblastoma and other cystic lesions remains challenging. Cortical dilation and perforation are two significant differential diagnostic points that cannot be observed on panoramic radiographs of ameloblastoma (Apajalahti et al. 2015). PR cannot facilitate a detailed examination, especially in patients with maxillary lesions, as the anatomy of the jaw and the overlapping teeth limit the diagnostic accuracy of two-dimensional PR (Vanagundi et al. 2020). In contrast, CT, which facilitates three-dimensional imaging, provides clinicians with more precise information about the lesions (Alves et al. 2018).

Cone-beam computed tomography (CBCT) has several other advantages over PR. Nevertheless, clinicians continue to use PR for the identification of ameloblastoma in the initial examination of patients despite the increasing use of CBCT and MRI (Wakoh et al. 2011; Cardoso et al. 2020).

PR is acquired during the initial clinical diagnostic process if the clinical symptoms are typical or only routine examinations are performed owing to the advantages of PR, such as the cost and ease of use.

Conventional computed tomography

PR is frequently utilised and labelled as recommended; however, as it yields two-dimensional images, it cannot be used for in-depth analysis. More precise and detailed information can be obtained from CT images. Thus, CT provides more resources than other radiological modalities and enables a clearer depiction of all anatomical components, especially the molars, the three roots of which frequently overlap in PR. CT also enables the modification and recreation of high-resolution pictures. CT enables a detailed analysis of the size, location, and internal structure of the lesion, as well as an assessment of whether the septa are separated. Lesions without loci may not be separated by septa. CT can be used to identify multilocular features (Alves et al. 2018).

CT shows the extent of the tumour more clearly than PR, (Cihangiroglu et al. 2002; Alves et al. 2018) which simplifies the process of selecting the optimal biopsy site. Buccolingual expansion, calcification, the presence of inner bone septa, perforation of the cortical bone, and root resorption can also be visualised on CT images. Furthermore, the diagnostic accuracy of CT images is higher than that of PR. As some of these features can only be visualised on CT images, CT is the only imaging modality that can be used to confirm their presence (Alves et al. 2018). The ability to determine the attenuation coefficient of the tissue being examined is another advantage of CT. The attenuation coefficient, which is correlated with tissue density, is a measure of the radiation absorbed by the structures being examined. The CT density patterns of ameloblastoma and odontogenic keratocysts have been determined using the density and heterogeneity on axial CT images. However, the density of odontogenic keratocysts was found to be lower than that of ameloblastoma. The presence of keratin in odontogenic keratocysts also increases the density on axial CT images, and odontogenic lesions, such as ameloblastoma and odontogenic keratocysts, can be evaluated based on these CT characteristics. Although the resulting CT density and heterogeneity can be used to explain the CT characteristics of various disorders more effectively, there is no definitive standard for differentiation (Crusoé-Rebello et al. 2009).

Cone-Beam computed tomography

CBCT has been the preferred imaging modality owing to several advantages, such as better spatial resolution, widespread availability, reduced cost, and lower radiation dose.

Soft tissue imaging with CBCT is subpar, making it impossible to determine the soft tissues surrounding the lesion. However, it facilitates the three-dimensional imaging of the cortical bone and bone structures (Apajalahti et al. 2015; Alves et al. 2018).

In contrast to conventional PR, CBCT yields three-dimensional images of the bone structure of the lesions and cortical bone and displays the internal bone structure of ameloblastoma, which is characterised by a honeycomb or soap bubble appearance (Apajalahti et al. 2015). Thus, the use of CBCT is beneficial as it enables the visualisation of the internal structure of the tumour and the distinct boundaries of the tumour, as well as the impact of the tumour on nearby structures. CBCT can identify the traits of various odontogenic lesions more accurately than PR, thereby providing accurate and trustworthy information for preoperative diagnosis, the formulation of treatment plans, and postoperative follow-up (Shokri et al. 2017; Li et al. 2018).

CBCT offers several advantages over three-dimensional imaging. For instance, oral contours can be visualised without overlapping structures or distorted or exaggerated images via CBCT. In addition, cysts can be identified more accurately on three-dimensional images owing to the accurate imaging of hard tissue enabled by CBCT. Moreover, CBCT is more cost-effective and convenient to use than other CT modalities and is associated with a lower radiation dose. Furthermore, CBCT is superior to PR in terms of diagnostic sensitivity and specificity (Cardoso et al. 2020; Surenthar et al. 2021).

Desmoplastic ameloblastoma can be differentiated using PR despite its resemblance with fibro-osseous tumours. CBCT can be used to obtain precise details regarding the internal structure. Distinct imaging characteristics of desmoplastic ameloblastoma, such as the honeycomb appearance owing to the presence of the coarse trabecular septum, can also be visualised using CBCT. CBCT can also be used to detect buccal/labial cortex expansion with perforation; thus, it can be used to differentiate desmoplastic ameloblastoma from fibro-osseous tumours (Luo et al. 2014). Furthermore, as CBCT is superior to PR in terms of evaluating lesions, convolutional neural network is superior to CBCT evaluations performed by physicians in the detection of ameloblastoma and keratogenic cysts; moreover, it is more accurate (Chai et al. 2021).

CT has enabled the visualisation of the radiological features of tumours and determining an optimal site for performing a biopsy. Nevertheless, clinicians should utilise texture analysis to assess CT images, as it may aid in avoiding unnecessary biopsies and hasten the development of alternate treatment strategies. CBCT is frequently used for clinical diagnosis, as it can circumvent issues such as overlap. Furthermore, the characteristics of the tumour are displayed more efficiently. The radiation dose and cost of CBCT are lower than those of other CT modalities. Thus, CBCT is recommended as an additional imaging examination when the clinical or two-dimensional features of a lesion make differentiation challenging. CBCT has been used to extract highly impacted third molars, in addition to diagnosing tumours, in clinical practice. CBCT imaging is often performed repeatedly to prevent harm to the nerves and other tissues.

Conventional magnetic resonance imaging

MRI has a higher soft-tissue contrast resolution compared with CT. MRI has been used to enable better visualisation of the internal and wall components of solid cavities (Konouchi et al. 2006; Hisatomi et al. 2011; Apajalahti et al. 2015; Vanagundi et al. 2020). Although CT provides details regarding the bone structure, not all recurrent tumours result in evident bone structure damage. Tumours may recur in the soft tissue at the site of the last surgery; MRI is a more effective imaging modality than CT in such cases (Kawai et al. 1998). Preliminary research suggests that MRI may be more suitable than CT for recognising recurrent disorders as it enables physicians to identify tissues by examining the proton composition. CT images reflect the electron density of the tissue (Heffez et al. 1988).

MRI has also been used to detect soft tissue around a lesion. Determining the anatomical relationship between the tumour and the peripheral nerve, particularly when it comes to avoiding the inferior alveolar nerve in patients with mandibular tumours, remains a challenge. MRI is particularly helpful in the detection of the inferior alveolar nerve. Michele et al. modified various MRI sequences to provide a more precise estimate of the distance from the inferior alveolar nerve and a more accurate representation of the anatomical structure to facilitate surgical therapy (Cassetta et al. 2014).

MRI may be more beneficial for identifying tumours that recur during the postoperative follow-up period. Recurrent tumours in the soft tissue can be recognised more easily owing to their superior soft tissue resolution. MRI also facilitates superior visualisation of the connection between the tumour and the surrounding soft tissue. Thus, MRI can be used to obtain more accurate data in cases with the mandibular tumour adjacent to the inferior alveolar nerve, thereby lowering the risk of nerve injury.

¹⁸F-fluorodeoxyglucose and ¹⁸F-fluorodeoxyglucose positron emission tomography

Ameloblastoma has a strong propensity to recur and may even spread to other areas if the resection is incomplete. Therefore, is crucial to identify recurrence at the earliest during the postoperative follow-up period. However, recurrence cannot be recognised solely via PR, CT, or MRI. ¹⁸F-FDG PET/CT plays an important role in the early recognition of recurrent or metastatic ameloblastoma. Consequently, ¹⁸F-FDG PET/CT imaging has been used for the detection of the metastasis of ameloblastoma in other organs (Nguyen 2005; Otsuru et al. 2008; Niu et al. 2013). Analysis of glucose metabolism in patients with ameloblastoma has revealed active glucose metabolism and absorption of a large amount of FDG by the tumour tissue. Moreover, the expression of the glucose transporter GLUT-1 was also observed in tumour cells. The active expression of GLUT-1 and the high FDG uptake reflect the proliferation and recurrence of ameloblastoma, respectively; however, the FDG uptake and expression of GLUT-1 were low in patients with unicystic ameloblastoma, reflecting low proliferation. Notably, the recurrence rate of unicystic ameloblastoma is the lowest in clinical practice (Otsuru et al. 2008).

¹⁸F-FDG PET/CT has demonstrated superior performance in the detection of the metastasis of ameloblastoma, suggesting that it can effectively detect metastatic tumours. Thus, performing ¹⁸F-FDG PET/CT during the postoperative follow-up period has been recommended to detect metastasis. However, ¹⁸F-FDG PET/CT is associated with high costs.

Fine-needle aspiration cytology

Fine-needle aspiration cytology (FNAC), a cytological technique used for identifying lesions, involves penetrating the lesion with fine needles and aspirating the contents of the lesion for cytological examination. FNAC has been widely used for identifying lymph node, salivary gland, thyroid, and parathyroid lesions since its introduction. Compared with other diagnostic techniques, FNAC is a simple, rapid, safe, cost-effective, and minimally invasive procedure, that is virtually painless. Moreover, it is associated with good patient comfort and does not require special equipment. Thus, FNAC can be performed safely in children and pregnant women.

FNAC requires sufficient material to be present within the lesion to be aspirated, and the assistance of a cytologist may be required in cases wherein the lesion size is small. Consequently, the type of facility and the skills and experience of the cytologist impact the sensitivity and specificity of the diagnosis (Günhan et al. 1989; Uçok et al. 2005; Gupta et al. 2018). Radiological diagnostic tools have been used to formulate surgical strategies for the majority of patients with cystic lesions. However, FNAC offers potential utility in preoperative diagnosis, in addition to elucidating the clinical and radiographic symptoms of the tumour. Preoperative cytological examination enables complete excision of the lesion without involving the margin and lowers the postoperative recurrence rate (Uçok et al. 2005; Perić et al. 2012; Thambi et al. 2012). The presence of clusters of basaloid cells in a myxoid background is the most important and characteristic cytological feature of ameloblastoma that can be used for determining the differential diagnosis (Perić et al. 2012; Desai et al. 2023). The FNAC aspirate comprises degeneration, myxoid changes, and hyalinisation, which represent the cells and stromal components of the tumour. Ameloblastoma can be diagnosed in early stages based on important cellular and stromal characteristics (Desai et al. 2023). Specific cells must be present in the cytological aspirate. Clusters of basaloid cells, followed by clusters of the other two cell types, are the most noticeable features. Notably, the contents of the FNAC aspirates obtained at two different time points varied in the study by Perić et al. Predominance of phagocytes lacking characteristic epithelial elements was observed in the FNAC aspirate acquired first, whereas predominance of basaloid cells was observed in the FNAC aspirate acquired subesquently (Perić et al. 2012).

Cytology has been used to diagnose granular ameloblastoma, the most aggressive type of ameloblastoma that requires maximal excision (Gupta et al. 2018). Although the histological subtype of ameloblastoma has no impact on the treatment strategy, cytological traits can aid clinicians in determining an appropriate course of action during the resection of lesions and while performing biopsies. Furthermore, benign tumours can be differentiated from malignant tumours via cytological analysis, thereby enabling patients to seek more effective treatment (Uçok et al. 2005; Desai et al. 2023).

FNAC presupposes adequate sampling modality and correct cytological and histopathological diagnoses. The acquisition of insufficient samples or the presence of atypical material in the aspirate may result in the absence of epithelial elements (Uçok et al. 2005; Perić et al. 2012). This may lead to false-negative results being obtained and the clinicians being misled.

Malignant tumour cells cannot be detected if the sampling is insufficient, and malignant lesions may be misclassified as conventional ameloblastoma consequently. This is particularly true for malignant or metastatic ameloblastoma and ameloblastic carcinomas, which are excessively large and do not enable further development into a widespread cyst. Thus, adequate and suitable sampling plays a crucial role in the differentiation of ameloblastic carcinoma from other lesions. Furthermore, cytologists must also maintain a high level of scepticism when making a diagnosis (Reid-Nicholson et al. 2009).

FNAC, a non-invasive diagnostic technique, can assist in the diagnosis of ameloblastoma. It aids in the preoperative and postoperative evaluation of ameloblastoma if an adequate amount of sample can be acquired to facilitate careful examination by experienced cytologists.

Cell blocks are created from the aspirated material after centrifugation, embedding in paraffin, sectioning, and staining. The diagnostic accuracy of FNAC is low. Comparison of the cytological smear with cell block technology and comparison of the smear and cell block technology with the histopathological diagnosis have revealed that cell block technology and histopathology results are more consistent. Aspiration of more liquid during the sampling process results in better cell production and higher diagnostic accuracy. Similarly, moving the needle back and forth in different directions may also increase production (Hallikeri et al. 2021). Cell block technology has assisted in the retention of cell structure and morphology. Moreover, it has benefits similar to those of FNAC. Thus, cell blocks offer additional data for the diagnosis. However, cell block technology is time-consuming and prone to material loss (Hallikeri et al. 2021; Zaidi et al. 2021).

Although it has some limitations, the use of FNAC is favoured in clinical practice. Cell block technology has been used as an adjunct to FNAC for diagnosing lesions in the jawbone. This can increase the precision of the diagnosis and assist in appropriate postoperative monitoring. FNAC is more cost-effective and simpler than imaging modalities. Furthermore, it is a more convenient and less invasive diagnostic method compared with biopsy. Although the sampling procedure has some restrictions, the operator must acquire a sufficient number of samples. Imaging examination can be paired with FNAC to determine the diagnosis if the physical condition of the patient is amenable. Care should be taken to ensure that adequate samples are acquired. A direct clinical diagnosis cannot be made using cell block technology.

Biopsy

An incisional biopsy is performed to determine the histological diagnosis following the detection of a mass in the jaws. Formulating an appropriate treatment plan for jaw cysts relies on the correct histological diagnosis. Biopsy of cystic lesions is performed to obtain lining tissue specimens representing the lesion. Thus, incisional biopsy, which aids in determining the next step of treatment, is performed as the first step in most cases of ameloblastoma. This step aids in avoiding the overtreatment of ameloblastoma and improves the aesthetic effect. Furthermore, it also enables the wide resection of the ameloblastoma, thereby eradicating the lesion (Gliddon et al. 2005; Perry et al. 2015). Regression of a large ameloblastoma has been observed following a biopsy in some cases (Hai 1988). Endoscopy is another important tool in the biopsy process that enables the acquisition of samples from the condylar neck and coronoid process, especially during the biopsy of large cysts. Endoscopy can also be performed in cases wherein the lesions are present in areas that are difficult to detect and sample (Gliddon et al. 2005). CT-guided percutaneous transthoracic lung biopsy, wherein a biopsy of the metastatic ameloblastoma can be performed percutaneously through the chest and lungs under CT guidance, and lymph node biopsy are important methods for confirming the diagnosis of metastatic ameloblastoma (Lin et al. 2014). Isolated epithelial islands with loosely arranged polygonal or polygonal cells in the central area that occasionally form cysts are characteristic histological features of ameloblastoma. The central region is surrounded by a layer of columnar cells with opposite nuclear polarity. However, the diagnosis of ameloblastic carcinoma may be missed if the biopsy site is not removed from the malignant site, resulting in a lack of evidence supporting the presence of a malignant tumour (Fahradyan et al. 2019).

Incisional biopsy is a good diagnostic technique for oral lesions. However, similar to other diagnostic techniques, the accuracy of incisional biopsy also varies. The diagnosis made on the basis of the findings of preoperative biopsy and the final diagnosis may differ in some cases. Sampling errors may occur during biopsy and result in undertreatment or overtreatment, as there are several different types of ameloblastoma (Renapurkar et al. 2022).

The discrepancy between the final diagnosis and results of incision biopsy may be attributed to the differences in histopathological expertise, insufficient tissue collection, and the presence of inflammation. Disparities in the diagnosis made by histopathologists may be attributed to the differences in specialty and subjectivity during the diagnostic procedure. The lack of an organisational structure may result in the acquisition of inadequate diagnostic specimens, whereas inflammation may impair histological interpretation (Chen et al. 2016).

It is advisable to integrate clinical and radiological signs to arrive at a diagnosis if an incisional biopsy is performed. Different biopsy procedures must be used as needed to acquire more typical samples. A second incision biopsy may have to be performed if the findings of the incision biopsy are discordant with the symptoms. Similarly, several specimens can be acquired from various locations to diagnose large lesions as the information obtained may be more thorough than that obtained from a single specimen. Additional information can be obtained based on the size and depth of the lesion tissue (Chen et al. 2016; Renapurkar et al. 2022).

Biopsy, which is an invasive diagnostic procedure that can be used for diagnosing ameloblastoma, has some limitations and must be performed after considering the health status and willingness of the patient. Therefore, biopsy is not performed if the diagnosis can be made using FNAC. However, FNAC is also performed in conjunction with radiological techniques to identify the type of tumour in some cases. The size of the tissue and biopsy site must be considered during the procedure.

Experimental/innovative diagnostic methods

Imaging systems

Spiral computed tomography

Spira CT has also been used in addition to CBCT to acquire three-dimensional images for the assessment of the oral cavity. The resolution of spiral CT is not adequate for evaluating dental lesions, and this affects the visualisation of the tissue present within the lesion (Meng et al. 2018). Spiral CT is expensive and radiation-intensive; nevertheless, it has been used in clinical practice owing to its ability to depict lesion locations from cross sections and multiple directions with good accuracy (Li et al. 2018). Multilayer spiral CT has been used to determine the range of jaw tumours and the changes in the bone (Yuan et al. 2008). However, multilayer spiral CT is inferior to CBCT in terms of the image quality of the fine structures in the maxillofacial region (Saati et al. 2017). The percentage of density increase (Enh%) obtained from dynamic multilayer spiral CT during the arterial stage has shown a significant correlation with microvessel density (MVD) in patients with ameloblastoma and odontogenic keratocyst. The Enh% and MVD were significantly higher in patients with ameloblastoma than those in patients with odontogenic keratocysts. These findings indicate that dynamic multilayer spiral CT can be an effective tool for discriminating ameloblastoma from odontogenic keratocysts (Hayashi et al. 2002).

However, spiral CT is not performed in patients who can undergo CBCT as it is more expensive, emits more radiation, and has lesser precision for depicting fine structures compared with CBCT.

Diffusion-weighted MRI

Ameloblastoma presents as a multilocular lesion with enhanced and non-enhanced solid cystic components, as well as increased surrounding cystic components. However, unicystic ameloblastoma may resemble dentigerous cysts and odontogenic keratocysts morphologically. Diffusion-weighted imaging (DWI) can be used to differentiate ameloblastoma from these lesions (Vanagundi et al. 2020).

DWI is a functional MRI technique that identifies different tissue components based on the Brownian motion of water molecules within the tissues. DWI has been used for the imaging of various head and neck diseases. The apparent diffusion coefficient (ADC) is a measure of the movement of water (Vanagundi et al. 2020). Physical and physiological characteristics, particularly physiological parameters, affect diffusion and changes in the physiological parameters may induce changes in the pixel intensities of the diffusion-weighted sequences (Sumi et al. 2008).

ADCs have been used to differentiate unicystic ameloblastoma without solid components from odontogenic keratocysts. The ADC of unicystic ameloblastoma was found to be significantly higher than that of odontogenic keratocysts in some studies, (Sumi et al. 2008; Han et al. 2018) and the accuracy of distinguishing ameloblastoma from dentigerous cysts and odontogenic keratocysts was 82% and 96%, respectively (Wamasing et al. 2022).

DWI can be used to diagnose odontogenic disorders; however, it lengthens the time to diagnosis. The considerable difference in the ADC values aids in the differentiation of ameloblastoma from other illnesses.

Dynamic contrast-enhanced MRI

Ameloblastoma has several histological characteristics. Unicystic ameloblastoma exhibits uniform and bright high signal strength on T2-weighted imaging and short tau inversion recovery, thereby indicating the water content within the internal components. Thus, differentiating these lesions from other cystic lesions is challenging. The use of contrast-enhanced MRI (CE-MRI) and dynamic contrast-enhanced MRI (DCE-MRI) for the diagnosis of ameloblastoma has proven to be beneficial (Asaumi et al. 2005; Hisatomi et al. 2011).

Solid components present as small areas of enhancement on contrast-enhanced T1-weighted imaging (CE-T1WI). Thicker edge enhancement is observed on CE-T1WI. Slight enhancement of some areas on DCE-MRI indicates the presence of solid components and/or intramural nodules with focal ameloblastoma tissue invasion. Pronounced enhancement of the tumour wall and intramural nodules, which are characteristic features of unicystic ameloblastoma, can be observed on CE-MRI and DCE-MRI. Therefore, the use of CE-MRI and DCE-MRI may aid in the differential diagnosis of unicystic ameloblastoma (Konouchi et al. 2006; Hisatomi et al. 2011).

The ADC value of ameloblastoma may be higher than that of odontogenic keratocysts on diffusion-weighted MRI in some cases. However, this method is time-consuming and unsuitable for clinical diagnosis. Similarly, DCE-MRI is used less frequently in clinical practices as it provides limited information.

Analytical methods applied in imaging systems

Convolutional neural network for panoramic radiography

Information can be acquired from only two-dimensional images in PR. Convolutional neural networks (CNNs), one of the most efficient deep learning structures, play a significant role in the field of medicine owing to the widespread use of AI in several fields. A CNN based on transfer learning has been used to retrieve features from PR to increase the diagnostic accuracy of ameloblastoma. CNN is capable of learning various types of data, particularly from two-dimensional images. Various levels of features can be extracted from several datasets. However, the capacity to extract features decreases as the size of the dataset decreases. Transfer learning has enabled the identification of high-level features in smaller datasets as it can perform the extraction process without requiring a large amount of data. The diagnostic accuracy of CNN is similar to that of physicians. Thus, the use of CNN for the screening of ameloblastoma would aid physicians (Poedjiastoeti and Suebnukarn 2018; Yang et al. 2020; Liu et al. 2021). Data enhancement technology can also be applied to increase the number of images in the dataset, thereby improving the diagnostic performance of CNN (Kwon et al. 2020). This technique can also add a parallel structure to conventional transfer learning to facilitate the simultaneous extraction of the characteristics of the two tumours. The diagnostic precision of CNNs has led to unprecedented advancement (Liu et al. 2021). Deep learning has shown promise in the detection of mandibular radiolesions, with a sensitivity of up to 90% (Ariji et al. 2019). Thus, its implementation as a diagnostic tool would aid physicians and also help distinguish odontogenic cysts or tumours from the Stafne bone cavity (Lee et al. 2021).

Clinicians can use artificial intelligence/CNN to extract features from panoramic radiographs and differentiate ameloblastoma based on the presence of these features. The advancement of artificial intelligence has enabled physicians to utilise CNN to extract imaging features from PR to boost diagnostic accuracy and develop treatment regimens; however, this method is unrealistic and rarely employed in clinical practice.

Texture analysis for MRI and CT

Texture analysis, defined as a quantitative analysis of images, extracts texture features from medical images. Pixels are the fundamental building blocks of an image. Texture analysis has also been used to identify the distribution of pixel signal intensity and the relationships between adjacent pixel values. High-dimensional data and subtle differences in the internal components of lesions can be retrieved via texture analysis. Most of these data cannot be observed by humans; however, they can be used to differentiate between different lesions, which in turn enables physicians to diagnose and treat patients with greater accuracy.

Texture analysis has been used in conjunction with CT to obtain additional information for the differential diagnosis of jaw cystic lesions. Different texture features can be used to assist in the non-invasive diagnosis of cystic lesions in the jaw, as the different cystic components present within the lesion show variations in texture properties. Texture analysis may even help avoid biopsy and accelerate the treatment process (Oda et al. 2019).

Texture analysis can also be performed in conjunction with MRI, in addition to the aforementioned MRI applications, which can be used to discriminate odontogenic keratocyst from ameloblastoma. Texture analysis has been used previously to differentiate benign tumours from malignant tumours in human patients. Texture analysis also facilitates the removal of the subjectivity of human vision from the quantitative evaluation of images. Entropy and the sum average are two texture parameters with statistically significant values. Entropy is defined as a measure of the degree of disorder between the pixels in an image, whereas the sum average is defined as a measure of the average value of the sum of two pixel values. Odontogenic keratocyst has lower entropy and total average values than those of ameloblastoma (Gomes et al. 2022).

 Molecular systems

Gene mutation and marker diagnosis

Incision biopsy is associated with a considerable error rate owing to the variations in the histological forms of ameloblastoma, particularly in cases of unicystic ameloblastoma or significant inflammatory infiltration. As the mechanism of gene mutation is better understood, BRAF V600E has been detected in 80% of patients with ameloblastoma but not in patients with other odontogenic cysts. Although the BRAF V600E mutation has not been detected in all patients with ameloblastoma, it can be used as an additional tool for differential diagnosis in some cases that are challenging to diagnose using conventional methods.

Sanger sequencing and quantitative real-time PCR are considered the most precise techniques for detecting mutations (Pereira et al. 2016; Sant'Ana et al. 2021). Immunohistochemistry (IHC) can also be performed using BRAF VE1 mutation-specific antibodies. The results of BRAF VE1 IHC are highly consistent with the mutation status of BRAF V600E, indicating that BRAF VE1 antibodies can be used to accurately predict the presence of BRAF V600E mutation. BRAF V600E can also be used to identify mandibular ameloblastoma and serves as a key marker for the disease. However, the application of this method in the maxilla is limited owing to the rarity of the incidence of BRAF V600E mutation (Mendez et al. 2022).

Several markers play important roles in the differential diagnosis, in addition to detecting mutated genes. These markers reflect the cell lineage and tissue origin of various lesions; therefore, they can be used for the differential diagnosis. For example, one such marker, cytokeratin, varies with the epithelial type (Joshi et al. 2015). Calretinin, a 29-kDa calcium-binding protein, is present in human tissues and tumours. However, calretinin is only detected in ameloblastoma among cystic odontogenic lesions. Thus, calretinin may be a specific marker and an auxiliary tool for differentiating ameloblastoma (Coleman et al. 2001).

Ameloblastoma can also be differentiated based on the cytokine content and the type of gelatinase in the cyst fluid. The levels of interleukin (IL)−1α and IL-1β were significantly lower in the cyst fluid of ameloblastoma; however, the IL-6 levels in the cyst fluid of ameloblastoma were higher than those in the cyst fluid of odontogenic keratocyst. No significant differences were observed in terms of tumour necrosis factor (TNF)-α levels in the cyst fluid.

Matrix metalloproteinases (MMP)−9, a type of MMP, is a gelatinase. Active MMP-9 is secreted by the inactive pro-MMP-9, and MMP-9 can degrade and remodel the extracellular matrix. Only a small amount of pro-MMP-9 has been detected in ameloblastoma. In contrast, pro-MMP-9 and its active form have been detected in most odontogenic keratocysts. This detection method can also be used for small cystic lesions as cytokines and gelatinase can be detected using 200 and 0.2 microlitres of cyst fluid, respectively (Kubota et al. 2001).

Gene mutation and marker content detection are time-consuming and expensive techniques that necessitate the use of specialised equipment and laboratory personnel. Furthermore, BRAF V600E mutations are uncommon in the maxilla. Therefore, it is not advisable to use cytokines or altered genes to detect lesions.

Gene mutation and biomarker changes have been used in laboratory research. Changes occurring in the macromolecular substances of upstream genomics are reflected in metabolomics. Thus, the impact of the mutation affects the downstream metabolites when BRAF V600E is mutated in ameloblastoma (Duarte-Andrade et al. 2019). Gene mutations are closely related to these metabolites. Therefore, future studies must aim to further improve the diagnostic rate of ameloblastoma and identify therapeutic targets for ameloblastoma.

Other methods

Ultrasonography

Soft tissue lesions in the head and neck can be diagnosed using ultrasonography. Ultrasonographic examination is a cost-effective, non-invasive, and simple examination technique that produces real-time images without exposing patients to ionising radiation or contrast agents. Ultrasonographic examination has been used to elucidate the differences between cystic and solid tumours and provide real-time data regarding blood flow within tumours. However, the examination of bone tissue is associated with some limitations. The internal structure of the bone is typically not visible in ultrasonographic imaging, which only depicts the external bone tissue. The mandible is compressed, and the cortical bone becomes thin as ameloblastoma continues to grow. Ultrasound can penetrate through the bone tissue, thereby enabling the imaging of these structures. However, ultrasonography is challenging to use in cases wherein the tumour size is small or the cortical bone is not thin. High-frequency ultrasonography cannot be performed in cases with large tumours, as the tumour size on the image will be smaller than the actual measurement. Ultrasonography has also been used to detect the presence of ameloblastoma in the mandible. Blood flow signals detected by colour Doppler flow imaging can determine the active proliferation of tumours. Abundant blood flow signals indicate active tumour proliferation (Lu et al. 2009; Shinohara et al. 2013).

Tomoelastography

Tomoelastography, a type of magnetic resonance elastography, produces high-resolution quantitative maps based on the mechanical properties of soft biological tissues, such as tumours. The measured stiffness and fluidity can be used to determine the presence, range, and neck lymph node metastasis of bone tumours. Tomoelastography provides important mechanical characteristics for the evaluation of bone malignancies (Beier et al. 2020).

Medical infrared thermography

The edge of the lesion must be removed to lower the recurrence rate. Routinely used radiological modalities may not define the surgical resection edge for smaller lesions or lesions without bone damage effectively. Clinical signs and palpation frequently fail to accurately locate the border of the tumour. Therefore, real-time imaging must be performed in such cases using medical infrared thermography (MIT), a non-invasive and non-ionised method. The thermal imaging technology used in MIT enables surgeons to clearly observe the progression of lesions in soft tissues. Surgeons can optimise the resection edge to prevent recurrence (when the temperature of the lesion area is typically higher than that of healthy tissue). Since it cannot be used for diagnosis, MIT is better suited for determining the edges of small lesions or other difficult-to-determine lesions. This has aided in lowering the recurrence rate (Delarue et al. 2021).

Ultrasonography is useful only in cases wherein the cortical bone within the lesion shows thinning. However, tomoelastography cannot be used to directly identify ameloblastoma owing to the mechanical properties of tomoelastography. Although MIT aids in surgical resection, it cannot be used as a diagnostic tool. The edges of small lesions are easier to visualise and tumours can be removed more precisely. Therefore, professionals must use medical infrared imaging during surgical resection.

Main differential diagnosis

Odontogenic keratocyst

Odontogenic keratocyst is the third most frequently occurring cyst in the oral cavity. The differences between the imaging findings of odontogenic keratocysts and those of ameloblastoma are negligible. Thus, it is difficult to distinguish ameloblastoma from odontogenic keratocysts. However, it is crucial to differentiate ameloblastoma from odontogenic keratocysts as the treatment approaches for ameloblastoma and odontogenic keratocysts vary.

Odontogenic keratocysts present as unilocular lesions with smooth margins, and more than half of these lesions occur in the maxilla. In contrast, ameloblastoma presents as a unilocular or multilocular lesion with a fan-shaped edge and often occurs in the mandible, which is more likely to cause resorption of the tooth roots and mobility or displacement of the tooth (Kitisubkanchana et al. 2020). The area with high density and bone expansion is the key to differentiating between these entities. The average bone expansion of ameloblastoma is greater than that of odontogenic keratocysts; however, high-density areas are observed only in odontogenic keratocysts. Lesions associated with impacted teeth can also be used to differentiate between the two lesions. Odontogenic keratocysts are more likely to be associated with impacted teeth (Ariji et al. 2011). The diagnostic accuracy of CT for the detection of ameloblastoma is usually higher than that of PR. Thus, the lesion is likely to be ameloblastoma if it presents as a multilocular lesion in the mandible with a scalloped border associated with root absorption and loosening or displacement of the tooth. Incisional biopsy and FNAC can be performed to exclude other diagnoses if the lesion is indistinguishable.

It is recommended to perform an incisional biopsy in the case of lesions associated with visible dilation. FNAC can be performed to determine whether the lesion is an odontogenic keratocyst if expansion is not observed (Chapelle et al. 2004).

Some of these markers can be used to differentiate these two entities. Unlike ameloblastoma, calretinin is not detected in odontogenic keratocysts. The detection of cytokines, such as IL-1 α, IL-1, and IL-6, as well as gelatinase, in the cyst fluid will also aid clinicians in determining the diagnosis.

Dentigerous cyst

Dentigerous cyst is another cyst that must be distinguished from ameloblastoma. In addition to ameloblastoma and odontogenic keratocysts, dentigerous cysts are also common odontogenic lesions. Almost all dentigerous cysts present as unilocular lesions during imaging. Ameloblastoma occasionally contains teeth and generally results in the resorption of the root; in contrast, the presence of the crown with an unerupted tooth is a typical imaging feature of dentigerous cysts (Meng et al. 2018). The diagnosis of dentigerous cyst must be considered in cases where the lesion contains only an unerupted crown and the site is related to the age of the patient. Histopathological examinations must be performed via an incisional biopsy to confirm the diagnosis.

Ameloblastic carcinoma is another disease that should be considered. Metastatic ameloblastoma usually exhibits the same characteristics as primary tumours and must be differentiated from other tumours that may occur at the metastatic site. However, ameloblastic carcinoma, a malignant tumour, differs from conventional ameloblastoma and exhibits typical malignant features, such as nuclear pleomorphism, mitotic abnormalities, and necrosis. These cytological features are the key to identifying ameloblastic carcinoma (Khalbuss et al. 2006; Reid-Nicholson et al. 2009; Nai and Grosso 2011). FNAC has achieved safety, simplicity, and high efficiency; however, great attention should be paid to the adequacy of sampling as it is a malignant tumour. Incorrect diagnosis may be obtained if typical and malignant cytological features are not obtained during aspiration.

Conclusion

Although ameloblastoma is a benign tumour, it is a locally invasive lesion. Similar imaging characteristics have been observed in other odontogenic lesions despite the variations in biological traits and therapeutic approaches in clinical practice. Careful differentiation of odontogenic lesions plays a key role in the development of surgical treatment plans.

PR is the most commonly used imaging technique for the detection of ameloblastoma; however, this technique typically only allows two-dimensional imaging and cannot provide detailed information. The use of CT and MRI for the diagnosis of oral tumours has increased significantly owing to the continued advancements in technology. CBCT yields three-dimensional images of bone structure, whereas MRI enables the visualisation of the characteristics of the soft tissue surrounding the lesion. FNAC and biopsy have been used to confirm the diagnosis of ameloblastoma. The diagnosis of ameloblastoma can be confirmed via gene mutation detection owing to the prevalence and specificity of BRAF v600E mutations, which are being developed continuously to provide insights into the molecular basis of ameloblastoma. Ameloblastoma can be diagnosed more accurately using different specialised techniques, such as cytokine levels, gelatinase species in the cyst fluid, ultrasonography, ¹⁸F-FDG PET/CT, tomoelastography, and MIT. Other diagnostic techniques may be selected, in addition to radiological examinations, to obtain more useful information about the lesion and establish a diagnosis of ameloblastoma if the diagnosis of ameloblastoma is uncertain.

Author contributions

Ke Hu and Xudong Zhang contributed to the conception and design of the study. Ke Hu carried out the literature search, produced the tables, and drafted the paper. Ruixue Chen and Xiangjun Li carried out the literature search, assessed the included literature. Xudong Zhang, Ruixue Chen and Xiangjun Li revised the manuscript for important intellectual content. Xudong Zhang approved the final manuscript. All authors agree to be accountable for all aspects of this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data sharing is not applicable to this article as no new data were created or analysed in this study.

Additional information

Funding

This study was supported by the Natural Science Foundation of Hebei Province, China [grant number H2021206165]. Hebei Provincial Department of Finance Project, PR China [grant number ZF2023016 and 361029].