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Lentigo Maligna — SCE Dermatology MCQ

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HardDermatological SurgeryLentigo MalignaSCE Dermatology

A 70-year-old man has a 4 cm irregularly pigmented macule on his left cheek that has been slowly enlarging over several years. Biopsy confirms lentigo maligna (melanoma in situ, lentigo maligna type). Due to the large size and facial location, staged excision is planned. What is the recommended staged excision technique?

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Correct answer: B — Slow Mohs or staged excision with mapped margin control using permanent (paraffin) sections, as frozen sections are unreliable for lentigo maligna

Lentigo maligna on the face poses unique surgical challenges: subclinical extension is common (often beyond clinically apparent margins), and standard frozen sections used in Mohs surgery are unreliable for detecting melanocyte atypia (melanocytes require special stains like MART-1/Melan-A on permanent sections). 'Slow Mohs' or staged excision uses mapped peripheral margins assessed on permanent (paraffin) sections with immunohistochemistry, with definitive reconstruction delayed until all margins are confirmed clear. This approach provides the best balance of complete excision and tissue conservation on the face. Standard 5-10 mm margins may be insufficient for large lentigo maligna due to subclinical spread.

Reference: BAD 2017 Melanoma Excision Margins; Mohs Society