Rethinking the Semantics of "Cutaneous Squamous Cell Carcinoma In Situ"

Abstract

Cutaneous squamous cell carcinoma in situ (cSCCIS) has a history of complex semantics. Historically, the term cSCCIS has been used for a range of distinct clinical and histopathological presentations, including arsenical keratoses, erythroplasia of Queyrat, and Bowenoid papulosis. Additionally, some consider actinic keratosis (AK) to be synonymous with cSCCIS, while others classify cSCCIS as an indolent, epidermal-confined intermediate between AK and well-differentiated cSCC. Certainly, “in situ” suggests a precursor lesion to invasive disease, and epidemiologic studies often pool cSCCIS and cSCC together. Here, we emphasize the clinical, histopathologic, and genetic differences between AK, which commonly progresses to well-differentiated cSCC, and cSCCIS, particularly the type often referred to as “Bowen disease (BD),” which can progress to “invasive BD”.