Postoperative Defect Size as a Criterion for Upstaging High-Risk Cutaneous Squamous Cell Carcinoma Treated With Mohs Micrographic Surgery.

Background: Brigham and Women's Hospital (BWH) criteria classify cutaneous squamous cell carcinoma (cSCC) with a preoperative (clinical) size ≥2 cm as high risk. However, the role of postoperative defect (histologic) size after Mohs micrographic surgery (MMS) in cSCC staging remains unclear.

Objective: To compare outcomes of cSCCs treated with MMS that have a clinical size <2 cm but a histologic size ≥2 cm with those clinically ≥2 cm.

Methods: Data were collected at a tertiary academic center. Patients with cSCC were followed for at least 33 months postoperatively. Recurrence, nodal involvement, metastasis, and disease-specific mortality were collectively analyzed as poor outcomes using multivariable logistic regression.

Results: Among 517 cSCCs, 216 were clinically ≥2 cm, and 301 were histologically ≥2 cm. Univariate analysis showed no significant differences between histologically ≥2 cm and clinically ≥2 cm cSCCs in recurrence or lymph node spread, although histologically ≥2 cm cSCCs were less frequently associated with disease-specific death ( p = .010) and metastasis ( p = .042). Multivariable logistic regression demonstrated that tumors histologically ≥2 cm did not have a significant difference in poor outcomes compared to those clinically ≥2 cm (OR [95% CI] = 0.37 [0.15-1.39]).

Conclusions: Postoperative defect size after MMS is a valid parameter for cSCC upstaging using BWH criteria.