Incidence of Squamous Cell Carcinoma in Situ Upstaged to Invasive Squamous Cell Carcinoma During Mohs Surgery

We sought to record the incidence and risk factors associated with upstaging squamous cell carcinoma in situ (SCCIS) to squamous cell carcinoma (SCC) during Mohs surgery with the largest sample size to date.

Patient records of preoperative biopsy-proven SCCIS being treated with Mohs between January 2019 to March 2022 were identified and reviewed. Postoperative diagnoses of invasive SCC proven by dermal infiltration on pathology were identified as upstaged SCCIS.

From 2,043 cases of preoperative diagnosed SCCIS, 47 (2.3%) were upstaged to SCC during Mohs surgery. Of the 47 invasive tumors, a large proportion on the hands (29.8%) and lesions with larger preoperative sizes had a higher risk of being upstaged to invasive SCC in this study.

All of the patients included were from rural and suburban areas of North Carolina. The only sections obtained were those reviewed for margin analysis, which may significantly underestimate the actual number of invasive SCC, as only the deepest and furthest portions were examined.

This retrospective study concluded that 2.3 percent of preoperatively diagnosed SCCIS were upstaged to SCC during treatment with Mohs surgery. Large lesions (>2cm) and lesions on the hand were more likely to be upstaged (29.8%). Treatment must be individualized considering the size of the lesion, the anatomic location, and the possibility that in some cases the initial biopsy may not have been able to accurately distinguish SCCIS from SCC. Although there is a myriad of treatment options for SCC, select patients with increased risk factors for upstaged SCC must be considered for margin assessed treatment modalities.