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Erythema Ab Igne — SCE Dermatology MCQ

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ModerateSkin CancerErythema Ab IgneSCE Dermatology

A 35-year-old woman has erythema ab igne on her anterior thighs from prolonged laptop use. She has been told it can rarely undergo malignant transformation. What type of cancer is associated with long-standing erythema ab igne?

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Correct answer: B — Squamous cell carcinoma (rarely, from chronic thermal damage)

Long-standing erythema ab igne (chronic heat-induced skin damage) can rarely undergo malignant transformation to squamous cell carcinoma, analogous to SCC arising in chronic burn scars (Marjolin ulcer). The chronic thermal damage causes DNA mutations in keratinocytes. Other rare sequelae include precancerous keratoses and Merkel cell carcinoma (very rarely reported). The SCC risk is low but the possibility underscores the importance of removing the heat source and monitoring long-standing erythema ab igne. Any indurated area, persistent ulceration, or nodule within erythema ab igne should be biopsied to exclude malignant change.

Reference: BAD 2019; DermNet NZ