Superficial spreading melanoma — SCE Dermatology MCQ

Correct answer: E — Excision biopsy with 2 mm clinical margin

The correct answer is E, excision biopsy with 2 mm clinical margin. A lesion with asymmetry, irregular border, colour variation and dermoscopic features of atypical network, irregular dots and regression structures is highly suspicious for melanoma, and full excisional biopsy with a narrow (2 mm) margin down to subcutaneous fat is the recommended diagnostic step. This approach removes the entire lesion for complete histological assessment while preserving accurate Breslow thickness measurement, which determines subsequent definitive margins and whether sentinel lymph node biopsy is indicated. Definitive wide margins are only applied once histology confirms the diagnosis and stage, per NICE NG14. Why the other options are wrong: B. Incisional biopsy from the darkest area: sampling only part of a pigmented lesion risks missing the area of deepest invasion, giving an inaccurate Breslow thickness and potentially understaging the tumour; it is reserved for large lesions or difficult anatomical sites where complete excision is not feasible. A. Cryotherapy because the lesion is small: destroys the lesion without any tissue for histology, so melanoma cannot be diagnosed, staged or excluded, and is never appropriate for a pigmented lesion suspicious of malignancy. C. Wide local excision before Breslow measurement: performing definitive wide margins before histological diagnosis and thickness are known leads to unnecessary tissue removal or an inadequate margin, and contradicts the staged NICE pathway of diagnostic excision followed by risk-stratified re-excision. D. Topical 5-fluorouracil for 6 weeks: a topical chemotherapeutic used for actinic keratoses and superficial basal cell carcinoma, with no role in invasive or suspected melanoma and no diagnostic value. Key point: Suspected melanoma requires complete excisional biopsy with a narrow 2 mm margin to establish diagnosis and Breslow thickness before any wider definitive excision is planned.

Reference: NICE Guideline NG14, Melanoma: assessment and management (updated 2022), Recommendations chapter, nice.org.uk/guidance/ng14/chapter/Recommendations