Subungual Melanoma — SCE Dermatology MCQ

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HardNail DisordersSubungual MelanomaSCE Dermatology

A 55-year-old woman presents with longitudinal melanonychia (a 4 mm wide brown-black band) of her right thumbnail. The band has widened over 6 months and there is pigment extension onto the proximal nail fold (Hutchinson sign). What is the most important differential diagnosis to exclude?

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Correct answer: C — Subungual melanoma

The best answer is “Subungual melanoma”. NICE bases melanoma diagnosis, excision margins and nodal assessment on complete histology, Breslow thickness, ulceration and clinical stage, with specialist review of suspicious or changing lesions. The alternatives “Nail matrix naevus”, “Racial melanonychia”, “Onychomycosis”, “Subungual haematoma” are clinically adjacent possibilities, but they do not fit the defining morphology, distribution, histopathology, risk signal or management sequence in this stem.

Reference: NICE NG14 melanoma recommendations: https://www.nice.org.uk/guidance/ng14/chapter/Recommendations