A clinicopathological analysis of 153 acral melanomas and the relevance of mechanical stress

Abstract

The pathogenesis of melanomas emerging in plantar surfaces remains unclear; however, mechanical stress has been reported to increase the formation of melanomas. In this study, we conducted a multicenter retrospective analysis of 153 acral melanomas diagnosed between 2000 and 2015 in Taiwan. The male-to-female ratio of the patients in question was 1:1.28, and the mean age at diagnosis was 68 years. We examined whether melanomas which developed in different areas of the patients' soles differed in their associations with various clinicopathological characteristics and survival. Testing by goodness of fit indicated that stress-bearing areas were significantly more conducive to the generation of melanomas than non-stress-bearing areas (P < 0.0001). More specifically, compared to the arch, the rear of the foot and front of the foot were significantly more conducive to the generation of melanomas (P < 0.0001 and P < 0.0001, respectively). The distribution pattern was not associated with differences in age, gender, right/left foot involvement, ulceration, mitosis, lymph node metastasis, tumor thickness, or stage. The overall, distant metastasis-free, and recurrence-free survival rates did not differ significantly between the stress-bearing and non-stress-bearing areas. Furthermore, while acral melanomas tended to develop on stress-bearing areas, the distribution pattern was not associated with the prognostic index or survival.

Figure 1

Distribution of acral melanomas in the plantar area. (a) The four areas of the sole are illustrated. The center of each lesion is marked and color-coded conforming to its Breslow thickness. (b) The number of lesion areas in each pixel is demonstrated on a color scale. Each pixel measures 5 mm by 5 mm. (c) Kaplan-Meier curves of survival in 114 acral melanomas. No overall survival differences were found between melanomas developed on stress-bearing and non-stress-bearing areas (P = 0.6, log-rank test).