Volar Location and Degree of Pigmentation Are Associated with Poor Survival and First Metastasis Pattern in Acral Melanoma

The risk factors affecting acral melanoma metastasis and prognosis remain unclear. The study included 168 patients with invasive acral melanoma who were followed for ≥3 years. We evaluated patient demographics, stages, clinicopathological features, anatomic site of melanoma including nail versus volar surface, and degree of melanoma pigmentations, sentinel lymph node biopsy results, and the first metastasis sites. Of the 168 patients (mean age 64.5 years; 52.4% male), 43 (25.6%) had invasive melanoma without metastasis, 113 (67.3%) had invasive melanoma with a first lymph node metastasis, and 12 (7.1%) had invasive melanoma with invasive melanoma with a first distant metastasis. Advanced T stage, high mitotic rate, ulceration, and the degree of pigmentation were significant risk factors for metastasis. Amelanotic and mild pigmentation of acral melanoma was associated with first distant metastasis, whereas heavy pigmentation was associated with first lymph node metastasis. Advanced TNM stages, high mitotic rate, volar location (hazard ratio = 2.24, 95% confidence interval 1.18-4.26), and low-pigmentation (hazard ratio = 2.02, 95% confidence interval 1.17-3.49) were associated with melanoma-specific mortality.