Interrater and Intrarater Reliability of Mohs Surgeons in the Assessment of MART-1 Frozen Section Margins for Melanoma

BACKGROUND – The use of Mohs micrographic surgery as a treatment for melanoma is rising, but the reliability of Mohs surgeons in assessing MART-1 melanoma en-face margins has not been evaluated.OBJECTIVE – To evaluate interrater and intrarater reliability of Mohs surgeons in interpreting margins of early-stage melanoma.METHODS – Twenty Mohs surgeons were asked to independently review images of frozen section MART-1 en-face peripheral margins of in situ or early-stage melanoma. Surgeons determined margins as positive or negative at initial evaluation and 6 weeks later. Primary outcomes were interrater and intrarater reliability.RESULTS – Interrater agreement was 84.1% (95% confidence interval [CI]: 75.5%–92.8%) for assessment 1 and 87.5% (95% CI: 78.4%–96.4%) for assessment 2, with kappa values 0.68 (95% CI: 0.50–0.82) and 0.75 (95% CI: 0.57–0.88). Average intrarater percent agreement was 95.0% (95% CI: 70.6%–100.0%) with average kappa 0.90 (95% CI: 0.50–1.00).CONCLUSION – Substantial interrater and nearly perfect intrarater agreement was identified among surgeons assessing melanoma margins utilizing MART-1 immunostaining, demonstrating consistent and reproducible assessment of melanoma margins during Mohs cases.