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Prognostic factors for melanoma include Breslow depth (BD), ulceration, and dermal mitotic rate (DMR). No studies have queried the effect of epidermal mitotic density (EMD) or atypical mitotic figure density (AMD) in an outcome-based assessment. Our objective was to determine if there is a relationship between EMD, AMD, BD, DMR, and ulceration and patient outcomes. This was a retrospective cohort study of 185 cases of thick and thin melanomas. Univariate and multivariate cause-specific regression analysis was performed. There was a positive correlation between EMD and BD ( P  = .0001). The difference between AMD in thick and thin melanomas was statistically significant. For every unit increase in EMD, patients had a 2.8-fold increase in the risk of distant metastasis; however, statistical significance was lost in the multivariate analysis. In adjusted analyses, ulceration, DMR, and BD were associated with outcomes. There were no statistically significant correlations between AMD and outcomes. This study is limited by its small sample size, diminution of the epidermis in some thick melanomas preventing EMD estimates, and reproducibility of mitotic figure counting. EMD and AMD do not seem to have any independent value in multivariate analyses for melanoma. Ulceration, BD, and DMR were significantly associated with outcomes and further solidify these known predictors of prognosis.

New American Joint Committee on Cancer eighth edition staging parameters have removed mitotic rate as a stage T1 category criterion, but it remains embedded in the synopsis of primary cutaneous melanoma (CM). A paucity of data is available, characterizing atypical mitotic forms in CM. In this study, we classify the various morphologic forms of atypical mitoses, characterize mitotic figure density, and examine the correlation between atypical mitotic figures and Breslow depth. We performed a retrospective study of 185 thick (>0.8 mm) and thin (<0.8 mm) CM specimens. Metaphase mitotic figures represented the highest percentage of total mitotic figures in cases of thick melanoma (40%) and were the second most common in thin melanoma (18%). The average Breslow depth for melanoma harboring starburst mitoses was 2.85 mm, compared with the average Breslow depth of all thick melanoma cases, 1.88 mm. The average thickness of melanoma cases containing tripolar mitoses was 2.28 mm. Breslow depth correlated with the number of atypical mitotic figures in both thick and thin melanomas (the Pearson correlation test, r = +0.18, P < 0.01). Metaphase and prophase mitoses are a common finding in both thick and thin melanomas. Although atypical mitoses were indiscriminate, starburst and tripolar (ie, multipolar) mitoses were only inherent to cases of thick melanoma (stage T3). In sum, our study reveals a parallel relationship between the density of atypical mitotic figures and Breslow depth.