Squamous Cell Carcinoma: Variants and Challenges
Squamous cell carcinoma (SCC) is the second most frequent form of skin cancer superseded by only basal cell carcinoma. Like basal cell carcinoma, SCC is predisposed for by excessive ultraviolet exposure, hence its association with advancing age and cumulative sun exposure, exposed anatomic sites and highest incidence in sunny geographic locales. The most important pathogenic mechanisms involve aberration of the p53 tumor suppressor gene via ultraviolet-induced mutation or HPV-encoded interdiction. The latter mechanism is thought to be the most important factor in the development of these malignancies in the setting of epidermodysplasia verruciformis and solid organ iatrogenic immunosuppression where multicentric tumor may present in a metachronous or synchronous fashion. Less common associations have been ascribed to chronic inflammatory or scarring conditions such as in the setting of burns, so called Marjolin’s ulcer, osteomyletic sinuses and lichen sclerosis et atrophicus, among others.