Concordance between a Mohs surgeon and a dermatopathologist in evaluating Mohs cryosections

Mohs micrographic surgery is the gold standard treatment for high-risk non-melanoma skin cancers. The success of Mohs relies on accurate histopathologic evaluation. Due to law restrictions in some European countries, Mohs surgeons are not permitted to report on histopathology; therefore, a pathologist evaluates the frozen sections.

To retrospectively assess the concordance between the certified Mohs surgeon and the pathologist in evaluating the Mohs slides that were intraoperatively evaluated by the pathologist.

Frozen section slides of a total of 237 Mohs cases between 2013 and 2020 were examined by the blinded Mohs surgeon, and the tumours were marked on copy maps. The copy maps and the original maps were compared, and the non-concordant cases were re-evaluated together by the Mohs surgeon and the dermatopathologist. The concordance rate was calculated, and the inter-rater agreement was statistically analysed using Cohen's Kappa coefficient.

We report a high concordance rate (97.9%) and inter-rater agreement (0.96) between Mohs surgeon and dermatopathologist in evaluating Mohs slides.

As a newly settled centre, our results are in alignment with experienced centres where the Mohs surgeon evaluates the slides herself and performs the surgery.