SCC in Chronic Dermatosis — SCE Dermatology MCQ

Correct answer: B — Malignant transformation in chronic inflammation (analogous to Marjolin ulcer concept)

The correct answer is B, malignant transformation in chronic inflammation (analogous to Marjolin ulcer concept). Squamous cell carcinoma arising within a longstanding psoriatic plaque reflects the same biological process seen in Marjolin ulcers, where persistent inflammation, chronic keratinocyte turnover, and cumulative DNA damage from reactive oxygen species create a field primed for malignant transformation. This is distinct from a named cutaneous "sign" of psoriasis; it is a recognised, if rare, long-term complication of chronic inflammatory dermatoses, and current UK guidance identifies chronic wounds, scars and inflamed skin as a genuine aetiological pathway for cSCC alongside UV damage. Any nodular, ulcerating or non-healing change within a chronic plaque warrants biopsy to exclude this transformation. Why the other options are wrong: C. Woronoff ring: this is a blanching halo of vasoconstricted skin surrounding a resolving psoriatic plaque, a benign vascular phenomenon with no link to malignancy. D. Auspitz sign: this describes pinpoint bleeding when psoriatic scale is removed, a diagnostic clinical sign of psoriasis, not a description of oncogenesis. E. Pathergy: this refers to skin lesions provoked by minor trauma, classically seen in Behcet disease and pyoderma gangrenosum, and is unrelated to malignant change in chronic plaques. A. Koebner phenomenon: this is the development of new psoriatic (or lichenoid) lesions at sites of skin trauma, explaining lesion distribution, not malignant transformation within an existing chronic lesion. Key point: unexplained ulceration, nodularity or non-healing change within a longstanding chronic dermatosis such as a psoriatic plaque should raise suspicion of malignant transformation (Marjolin-type change) and prompt biopsy, distinct from the named clinical signs of psoriasis itself.

Reference: British Association of Dermatologists guidelines for the management of people with cutaneous squamous cell carcinoma 2020, British Journal of Dermatology (Keohane et al., 2021), https://onlinelibrary.wiley.com/doi/10.1111/bjd.19621