Mitotic rate is a more reliable unfavorable prognosticator than ulceration for early cutaneous melanoma: A 5-year survival analysis

Abstract

The presence of ulceration has been considered as one of the most important primary tumor characteristics of cutaneous malignant melanoma (CMM) for predicting patient outcome. Yet recently, scientific attention has been drawn towards another microscopic feature of primary tumors, the mitotic rate (MR). The present study aimed to examine the relationship between the presence of ulceration and the mitotic rate and clinicopathological characteristics and melanoma patient survival, and to discuss the results in the context of AJCC melanoma staging recommendations. Tissue samples were obtained from 104 patients treated for CMM. In classical H&E staining, the mitotic rate and the presence of ulceration were evaluated. Non-mitogenic tumors were defined as having 0 mitoses/mm2, low mitogenic potential, 1-2 mitoses/mm and highly mitogenic tumors, ≥3 mitoses/mm2. In the entire group of 104 patients, a high mitotic rate (hMR) and ulceration were highly negative prognostic factors, and indicated considerably shorter overall survival, cancer-specific overall survival and disease-free survival. Notably, hMR appeared to have a statistically significant negative impact on survival in early melanomas in both the pT1 (P=0.001) and pT2 subgroups (P=0.006). Kaplan-Meier analysis of the remaining subsets (pT3 and pT4) did not reveal any important differences in the 5-year survival with regard to MR values. The presence of ulceration also had a prognostic significance for early melanomas, but only for pT1 tumors (P=0.05). Multivariate analysis confirmed that hMR was strongly associated with an unfavorable prognosis. Ulceration had no prognostic significance in the Cox proportional hazards model. Considering the biology of melanoma, hMR seems to be a more reliable parameter than the presence of ulceration. The value of MR categorizes melanomas into tumors with low or high proliferative potential, thus giving direct information concerning their capacity to infiltrate deeper layers of the dermis and, potentially, to generate regional lymph node and distant metastases.