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CUP — SCE Medical Oncology MCQ

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ModerateCancer of Unknown PrimaryCUPSCE Medical Oncology

A 55-year-old man presents with poorly differentiated carcinoma in an axillary lymph node. CT shows no other sites of disease. Immunohistochemistry is negative for all lineage markers except focal S100 positivity. What should be done before classifying this as cancer of unknown primary?

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Correct answer: B — Extensive PET-CT, testicular ultrasound, serum AFP/HCG/LDH, melanoma markers review, and dermatological assessment

Before labelling a tumour as CUP, a thorough clinicopathological workup is mandatory. Focal S100 positivity raises the possibility of melanoma (though S100 is not specific). Additional melanoma markers (Melan-A, HMB-45, SOX10) should be tested. In a male with axillary adenopathy, testicular examination and tumour markers (AFP, HCG, LDH) are essential to exclude germ cell tumour. PET-CT may identify an occult primary in approximately 25-40% of cases. Dermatological assessment for regressed melanoma is also important.

Reference: NICE NG36 Cancer of unknown primary; ESMO 2024 CUP Guidelines