Additional review of Mohs slides to optimize Mohs micrographic surgery.

BACKGROUND: One significant risk factor for recurrence after Mohs surgery is misinterpretation of slides.

OBJECTIVES: To determine how often pathologists detected incompletely excised basal cell carcinoma (BCC) on Mohs slides and to determine risk factors for incompletely excised BCCs.

METHODS: This retrospective study included 1653 BCCs treated with Mohs surgery in a university hospital between 2007 and 2011. For routine quality assurance, all slides were additionally reviewed by a pathologist within 1 week of the procedure. For this study, all cases that had divergent interpretations were re-evaluated by a Mohs surgeon and a pathologist. Mixed-effects logistic regression models with Mohs surgeon effects as random effects were used to determine risk factors for incompletely excised BCC.

RESULTS: Incompletely excised BCCs were detected in 31 cases (2%), in which defects > 20 mm in diameter were an independent risk factor (odds ratio 3.58, 95% confidence interval 1.55-8.28). Other studied variables (i.e. aggressive subtype, previously treated BCC, location on nose and > 2 Mohs stages) did not affect the risk of incompletely excised BCCs.

CONCLUSIONS: The additional review of Mohs slides might increase accurate interpretation, especially in large BCCs.