Different mitotic rates are associated with different prognostic factors, relapses, and survival rates in melanoma.

Background: Mitotic rate is one of the major prognostic factors in melanoma.

Objective: To investigate the significance of mitotic rate and possible impacts of clinicopathological factors on the course of all staged melanoma patients.

Methods: A total number of 970 melanoma patients were analyzed. Mitotic rates were grouped for analysis as follows: 0-1, 1.1-4.9, 5-9.9, and ≥10 mitoses/mm .

Results: Melanomas with higher mitotic rates were more likely to be associated with nodular histology (P = 0.0001), higher Clark level (P = 0.0001), thick Breslow depth (P = 0.0001), ulceration (P = 0.0001), vertical growth pattern (P = 0.0001), neurotropism (P = 0.04), lymphovascular invasion (P = 0.01), de novo melanoma (P = 0.0001), absence of tumor infiltrating lymphocytes (P = 0.02), advanced stage (P = 0.0001), and relapse (P = 0.0001). The 5-year overall survival (OS) rate of all patients was 68.7%, and it decreased significantly from 87% in melanomas with 0-1 mitoses/mm to 65.2%, 56.6%, and 50.4% in melanomas with 1.1-4.9, 5-9.9, and ≥10 mitoses/mm , respectively (P = 0.0001). Age (P = 0.04), gender (P = 0.03), histology (P = 0.0001), Clark level (P = 0.001), T-stage (P = 0.003), ulceration (0.006), node involvement (P = 0.0001), metastasis (P = 0.005), and relapse (P = 0.0001) were correlated with OS in 0-1 mitoses/mm melanomas, whereas lymphovascular invasion (P = 0.0001), BRAF mutation (P = 0.01), metastasis (P = 0.0001), relapse (P = 0.0001), and relapse pattern (P = 0.005) were found significant for ≥10 mitoses/mm melanomas.

Conclusion: Higher tumor mitotic rates associated with known histopathological and clinical poor prognostic factors were found to be significantly independent predictors of early relapse and unfavorable survival for cutaneous melanoma patients. Moreover, different prognostic variables were found to be affecting survivals in melanoma patients with lower and higher mitosis.