Invasion risk of cutaneous squamous cell carcinoma in situ by histological subtype: a retrospective cohort study
Aims Cutaneous squamous cell carcinoma in situ (SCCis) can be classified histopathologically into four subtypes: full-thickness (FT), hypertrophic actinic keratosis (HAK), Bowenoid, and acantholytic types. 3%–5% of SCCis lesions progress to invasive squamous cell carcinoma (iSCC), however progression risk by subtype has not been assessed. Aim one of this study is to quantitatively assess the risk of iSCC associated with each histological subtype of SCCis. Aim two is to evaluate if the histological grade of iSCC differs among subtypes of the associated SCCis. Methods The pathology information system at our institution was queried for cutaneous SCCis cases with and without associated iSCC from 2020 to 2022. The study group consisted of 65 cases of SCCis with associated iSCC and control group 65 randomly selected cases of SCCis without invasion. For each case SCCis subtype was classified as FT, HAK, Bowenoid or acantholytic type. iSCCs were classified as low grade if well to moderately di
