Muir-Torre Syndrome — SCE Dermatology MCQ

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HardSkin CancerMuir-Torre SyndromeSCE Dermatology

A 48-year-old man presents with a sebaceous carcinoma of his eyelid. He has a personal history of colorectal carcinoma at age 40. Immunohistochemistry of the sebaceous carcinoma shows loss of MSH2 protein expression. What genetic syndrome does this indicate?

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Correct answer: C — Muir-Torre syndrome (Lynch syndrome variant)

Loss of mismatch repair (MMR) protein expression (MSH2, MLH1, MSH6, PMS2) on immunohistochemistry of a sebaceous neoplasm is diagnostic of Muir-Torre syndrome — a phenotypic variant of Lynch syndrome (hereditary non-polyposis colorectal cancer/HNPCC). The combination of sebaceous neoplasm + personal history of colorectal cancer at young age (<50) + MMR protein loss is classic. Affected patients require colonoscopic surveillance, endometrial screening, and monitoring for other Lynch-associated cancers (genitourinary, gastric, ovarian). First-degree relatives should be offered predictive genetic testing. Microsatellite instability (MSI) testing on the tumour tissue provides additional diagnostic confirmation.

Reference: BAD 2021; NICE NG151 Colorectal Cancer; Lynch Syndrome Guidelines