Risk factors for complicated Mohs surgery in the South Sweden Mohs Cohort.

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.

Surgical treatment of basal cell carcinoma: a case series on factors influencing the risk of an incomplete primary excision.

BACKGROUND: Basal cell carcinoma (BCC) is the most common skin cancer form, and one first-line treatment is surgical excision. Complete excision is vital to minimize risk of recurrence. Studies on occurrence of incomplete excisions have given diverse results and seldom include large populations from a dermatological setting. OBJECTIVES: The rate of positive surgical margins in primary surgery of BCC at a tertiary dermatology clinic is studied. Factors associated with an incomplete primary excision are analysed. METHODS: Patients scheduled for standard excision, without perioperative margin control, of BCC during the years 2008-2015 were prospectively enrolled in the study. Tumour-specific factors, including histopathologic subtype, as well as postoperative outcome were registered. Incomplete excisions were analysed in relation to patient- and tumour-related factors. RESULTS: In total, 4.6% of 3911 BCC tumours were incompletely excised. The rate of incomplete excisions was higher for facial tumours and among tumours with an aggressive histological subtype. Morpheiform BCC on the nose or ear had the highest rate of an incomplete excision, 61.5% and 50%, respectively. CONCLUSIONS: Most BCCs, irrespective of subtype, were completely excised during the primary excision. Tumour sites nose and ears were associated with the highest rate of positive primary surgical margins, especially for infiltrative or morpheiform BCCs. Surgery with perioperative examination of margins is strongly recommended for these tumours.