Squamous Cell Carcinoma — SCE Dermatology MCQ

Correct answer: E — Chronic wound and scarring

The correct answer is E, chronic wound and scarring. In dystrophic epidermolysis bullosa, repeated cycles of blistering, ulceration and abnormal wound healing create a persistently inflamed, fibrotic dermal environment that drives malignant transformation of keratinocytes, producing the classic Marjolin ulcer type of squamous cell carcinoma. This mechanism is distinct from UV carcinogenesis: RDEB associated SCC arises on non-sun-exposed sites such as the dorsum of the foot, exactly as in this stem, and behaves aggressively with high rates of local recurrence and metastasis. UK best practice guidelines for EB identify chronic non-healing wounds as the dominant oncogenic driver, recommending biopsy of any wound that fails to heal or changes in character. The 20-year disease duration and site (chronically ulcerated dorsum of foot, not sun-exposed) are the discriminating clues pointing to chronic wound related carcinogenesis rather than UV damage. Why the other options are wrong: A. UV exposure: the dorsum of the foot in this patient is a site of chronic ulceration, not one selected for cumulative UV damage, and EB-SCC characteristically arises at sites of blistering rather than sun-exposed skin. D. Immunosuppressive medication: there is no history of transplantation or immunosuppressive therapy here, and this is a recognised risk factor for SCC in organ transplant recipients, not in EB. B. HPV infection: HPV is implicated in some anogenital and periungual SCCs but is not the established driver of SCC in dystrophic EB, where chronic wounding and fibrosis are causative. C. Smoking: smoking increases SCC risk mainly at mucosal and lip sites through direct carcinogen exposure and is not relevant to wound-related SCC pathogenesis in EB. Key point: In dystrophic epidermolysis bullosa, SCC arises from chronic wound and scar related inflammation and fibrosis (Marjolin ulcer mechanism), not UV exposure, so any non-healing EB wound warrants biopsy.

Reference: Mellerio JE, Robertson SJ, Bernardis C, et al. Management of cutaneous squamous cell carcinoma in patients with epidermolysis bullosa: best clinical practice guidelines. British Journal of Dermatology 2016;174(1):56-67. https://onlinelibrary.wiley.com/doi/10.1111/bjd.14104