The diagnostic challenges of patients with carcinoma of unknown primary

ABSTRACT

Introduction

Cancer of unknown primary (CUP) is a disease entity encompassing heterogeneous malignancies without a clinically-detectable anatomical primary. It is usually a poor prognosis malignancy with dismal prognosis where molecular and genetic testing were expected to be a major breakthrough.

Areas covered

In this review, we provide an overview of the advances in the understanding of the carcinogenesis, biology, diagnosis and treatment of patients with CUP. This review focuses on the advantages and inconveniences of immunohistochemistry and CUP classifiers in assessing the progress in the management of CUP.

Expert opinion

CUP classifiers were expected to gradually replace the classical multistep approach in identifying the culprit tumors to guide site-specific therapy. Immunohistochemistry staining led to the prediction of a single tissue of origin in 10.8–51%. CUP classifiers identified the primary site in 61–89% of these cases and were concordant with immunohistochemistry in 57.1–100%. Immunohistochemistry is cheap, fast and broadly available whereas CUP classifiers are less widely available and have not been validated in randomized control trials. The diagnostic recommendations consist of a standard pathology evaluation based on morphology and algorithmic immunohistochemistry assessment. Physicians should weigh in the input of the CUP classifier to the clinical picture and pathology investigations before performing additional investigations.

KEYWORDS:

• Cancer of unknown primary
• diagnosis
• molecular diagnosis
• immunohistochemistry
• tailored therapy
• site-specific therapy
• biomarker-guided therapy
• targeted therapy
• empiric chemotherapy

Article highlights

• CUP is an enigmatic disease entity of heterogeneous malignancies without a detectable primary despite adequate workup.

• CUP is usually a poor prognosis malignancy with dismal prognosis where molecular and genetic testing were expected to be a major breakthrough.

• The advances in the molecular era allowed a better understanding of the biology and diagnosis of CUP but it did not translate into a survival benefit.

• Physicians should weigh in the input of the CUP classifier to the clinical picture and pathology investigations before performing additional investigations.

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 paper received no funding.