Abstract

There are limited data regarding difference in growth pattern between acral melanoma and non-acral melanoma. We defined acral melanoma as melanoma arising from the volar areas in hands and feet and nail apparatus. We excluded the patients whose prediagnosis duration or excisional specimens was not available. We also excluded cases that horizontal diameter could not be evaluated in excisional specimens. We finally included 249 cases of acral melanoma and 243 cases of non-acral melanoma. The demographic difference was not significant between two groups. Although prediagnosis duration was longer and advanced stage was more common in acral melanoma than non-acral melanoma, vertical growth phase was more common in non-acral melanoma than acral melanoma. Whereas horizontal diameter is longer in acral melanoma than non-acral melanoma. Dissemination to lymph node was more common in acral melanoma. Lymph node involvement was associated with deeper Breslow thickness in non-acral melanoma but not in acral melanoma. The degree of correlation with prediagnosis duration was remarkable with horizontal diameter in acral melanoma, but with Breslow thickness in non-acral melanoma. Overall survival was worse in acral melanoma than non-acral melanoma. The prognostic value of Breslow thickness was more remarkable in non-acral melanoma than acral melanoma. In conclusion, acral melanoma has longer radial growth phase compared to non-acral melanoma. However, acral melanoma is more commonly associated with lymph node dissemination, which contributed to wore survival in acral melanoma than non-acral melanoma. Further studies including molecular analysis would be helpful to elucidate these differences in growth pattern between acral and non-acral melanoma.

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