Active surveillance of low-risk papillary thyroid microcarcinomas in Japan and other countries: a review

ABSTRACT

Introduction: Active surveillance of low-risk papillary thyroid microcarcinomas (PTMCs) was initiated in Japan in 1993 and has since been adopted in many countries, especially after its approval by the American Thyroid Association in 2015.

Areas covered: We performed a literature review in Medline/PubMed to identify studies that used active surveillance for PTMCs. Moreover, we performed a literature review about the increased incidence of thyroid microcarcinomas in relation to the relative stability of deaths due to thyroid carcinomas.

Expert opinion: No patients showed life-threatening metastasis/recurrence or died of thyroid carcinoma during active surveillance or after conversion surgery following PTMC progression. Thus, active surveillance should be the first-line management of PTMCs without high-risk features. In the future, molecular testing of actively growing PTMCs using cytology specimens could be useful to guide the treatment plan.

KEYWORDS:

• Active surveillance
• age
• growth activity
• papillary microcarcinoma
• thyroid carcinoma

Article highlights

• Most PTMCs do not rapidly or constantly grow but are stable, slow-growing, or may even shrink.

• Under appropriate active surveillance, conversion surgery after the detection of progression signs is not too late.

• No patients showed life-threatening metastasis/recurrence or died of thyroid carcinoma during active surveillance or after conversion surgery.

• Immediate surgery may be more straightforward than active surveillance. However, the incidence of unfavorable events was significantly higher in the immediate surgery group than in the active surveillance group.

• Evaluation of tumor growth based on maximal diameter is more appropriate than evaluation based on tumor volume.

• Evaluation based on tumor growth is simpler and, according to the experience of Japanese patients, no patients showed significant metastases during active surveillance.

• Since only a small portion of PTMCs grow during pregnancy, PTMCs in young women are candidates for active surveillance. Even though they grow during pregnancy, surgery after delivery is not too late.

• PTMCs attached to the tracheal cartilage are candidates for active surveillance unless the angles formed by the tracheal cartilage and the tumor surface are obtuse.

• PTMCs on the dorsal side of the thyroid are candidates for active surveillance unless they are located along the recurrent laryngeal nerve.

• To date, no biological or molecular markers have been identified for predicting the growth activity of PTMCs at the time of cytology.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This study was not funded.