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CUP Inguinal Adenocarcinoma — SCE Medical Oncology MCQ

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ModerateCancer of Unknown PrimaryCUP Inguinal AdenocarcinomaSCE Medical Oncology

A 60-year-old man presents with cancer of unknown primary — isolated inguinal lymphadenopathy containing adenocarcinoma (not squamous). IHC shows CK7+, CK20+, CDX2 weakly positive. PSA negative. Where should the primary search focus?

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Correct answer: B — GI tract (colorectal/appendiceal) or bladder/urethra — CK7+/CK20+ with CDX2 positivity suggests GI origin; cystoscopy and colonoscopy are priority investigations

Adenocarcinoma in inguinal lymph nodes with CK7+/CK20+ and CDX2 weak positivity suggests a GI origin (colorectal, appendiceal, or anal glandular). The inguinal drainage territory also includes the bladder/urethra, vulva/vagina, and lower limb skin. Priority investigations include: colonoscopy (including careful appendiceal assessment), cystoscopy, PET-CT and CT thorax/abdomen/pelvis. Treatment should be guided by the most likely tissue of origin if no primary is identified.

Reference: NICE NG36 CUP; ESMO 2024 CUP Guidelines