Is the prognosis and course of acral melanoma related to site-specific clinicopathological features?

Acral melanoma is an uncommon type of melanoma in Caucasian patients. However, acral melanoma is the most common type of melanoma in African and Asian patients. Comparison analyses between hand-acral melanoma and foot-acral melanoma have been rarely reported in the literature. Acral melanoma is an uncommon melanocytic tumor characterized by an intrinsic aggressiveness, with specific histological and clinicopathological features. Acral melanoma involves the palms, soles and sub-ungueal sites.

A total of 244 patients with acral melanoma were included in our analysis. The current study was performed in three different medical centers: Sapienza University of Rome, San Gallicano Institute of Rome and University of Magna Graecia (Italy). The Kaplan-Meier product was used to estimate survival curves for disease-free survival and overall survival. The log-rank test was used to evaluate differences between the survival curves. Assuming that the effects of the predictor variables are constant over time, the independent predictive factors were assessed by Spearman's test and subsequently data were analyzed performing Cox proportional-hazard regression.

In both univariate and multivariate analyses Breslow thickness (p < 0.0001) and ulceration (p = 0.003) remained the main predictors. General BRAF mutation was detected in 13.8% of cases. We found that median Breslow value and the percentage of recurrences were similar in hand-acral melanoma and foot-acral melanoma, as well as there were no differences in both short and long-term.

The absence of differences in survival between hand-acral melanoma and foot-acral melanoma shows that the aggressiveness of the disease is related to distinct mutational rate, as well as to anatomical site-specific features, rather than to the visibility of the primary lesion.