Chapter 4 Additional review of Mohs slides to optimize Mohs micrographic surgery
Background: One significant risk factor for recurrence after Mohs micrographic surgery (MMS) is misinterpretation of slides. Objectives: To determine how often pathologists detected incompletely excised basal cell carcinoma (BCC) on MMS slides and to determine risk factors for incompletely excised BCCs. Methods: This retrospective study included 1,653 BCCs treated with MMS in a university hospital between 2007 and 2011. For routine quality assurance, all slides were additionally reviewed by a pathologist within one week of the procedure. For this study, all cases that had divergent interpretations were re-evaluated by a MMS surgeon and a pathologist. Mixed-effects logistic regression models with MMS surgeon effects as random effects were used to determine risk factors for incompletely excised BCC. Results: Incompletely excised BCCs were detected in 2% (31/1,653), in which defects > 20 mm in diameter were an independent risk factor (OR 3.6, 95% CI 1.6-8.3). Other studied variables (i.e. aggressive subtype, previously treated BCC, location on nose and > 2 MMS stages) did not affect the risk of incompletely excised BCCs. Conclusions: The additional review of MM slides might increase accurate interpretation, especially in large BCCs. 2 Erasmus Medical Center Rotterdam