Does mitotic rate predict sentinel lymph node metastasis or survival in patients with intermediate and thick melanoma?

Background: The significance of mitotic rate (MR) in melanoma remains controversial.

Methods: In this retrospective analysis of a prospective randomized trial that included patients with melanoma of 1.0 mm or greater, all patients underwent wide excision and sentinel node (sentinel lymph node [SLN]) biopsy. Univariate and multivariate analyses were performed to evaluate factors predictive of disease-free survival (DFS) and overall survival (OS).

Results: A total of 551 patients had MR reported. A cut-off point of 6 mitoses/mm(2) best discriminated DFS and OS: 455 patients (82.6%) had MR less than 6/mm(2). SLN were tumor-positive in 14.7% of low MR versus 31.3% of high MR patients (P = .0003). There were significant differences in DFS (P = .0014) and OS (P = .0002) between the 2 groups, however, MR failed to remain significant in the multivariate model.

Conclusions: MR is weakly predictive of SLN status but it is not an independent predictor of survival for melanomas 1.0 mm or thicker.