Frequency of squamous cell carcinoma (SCC) invasion in transected SCC in situ referred for Mohs surgery: the Dartmouth-Hitchcock experience.

Abstract

Squamous cell carcinoma (SCC) in situ may be transected in a superficial biopsy, which makes it difficult to distinguish between in situ and invasive carcinoma. This study investigated the frequency of invasive SCC in transected SCC in situ referred for Mohs surgery. A retrospective chart review was performed to identify subjects with biopsy-proven, transected SCC in situ referred for Mohs surgery. The incidence of invasion, histologic variables, preoperative and intraoperative correlations, and clinical factors were determined and recorded. Of 51 cases identified, five (9.8%) were found to harbor invasive SCC, 15 (29.4%) showed SCC in situ, and 28 (54.9%) showed evidence of scarring, inflammation, or actinic keratosis at the prior biopsy site. Invasive lesions required significantly more stages of Mohs surgery to obtain tumor clearance but were similar with regard to patient age, symptoms, and family and personal histories of skin cancer. Preoperative lesion size and duration were greater in invasive cases, but these differences did not reach statistical significance. A small number of transected SCCs in situ, to which the caveat "invasion cannot be ruled out" can be applied, have an invasive component that is identified during Mohs surgery. Definitive treatment choices should depend on the physician's impression, the clinical characteristics of the lesion, tumor location, patient comorbidities, and patient desires.