Carolina Nätterdahl

Background Mohs micrographic surgery (MMS) is a precise, tissue‐sparing surgical technique that offers superior cure rates compared to traditional surgical excision. However, the degree of difficulty of MMS depends on many variables, and consequently, the number of surgical stages required for each case is quite unpredictable. Objectives To identify risk factors for complicated MMS, defined as MMS requiring ≥3 stages. Methods In a cohort study design, data were prospectively collected from 612 patients that underwent MMS for basal cell carcinoma (BCC) at the Department of Dermatology, Skåne University Hospital, Lund, between 2009 and 2020. Univariate and multivariate logistic regression were used to estimate the risk of MMS requiring ≥3 stages. Due to the risk of multicollinearity between recurrent or incompletely excised BCC and previous treatments, a partially and a fully adjusted multivariate logistic regression model were constructed. Results In fully adjusted multivariate analyses, age (odds ratio (OR) 1.02; confidence interval (CI) 95% 1.00–1.04), previous cryotherapy (OR 2.3; CI 95% 1.1–4.8), and >1 previous surgery (OR 3.4; CI 95% 1.5–7.7) were significantly associated with risk of complicated MMS. Recurrent BCC was associated with the risk of complicated MMS in partially adjusted multivariate analyses, but not in the fully adjusted analyses. In this highly selected cohort, histopathological subtype, and tumour localization were not associated with the risk of complicated MMS. Conclusions Older age and tumours previously treated with cryotherapy or multiple prior surgeries increased the risk of MMS requiring ≥3 stages. Whether recurrent BCC is an independent risk factor for complicated MMS needs further evaluation. Knowledge of these risk factors may ameliorate the planning of Mohs surgeries.