Acral lentiginous melanoma versus other melanoma: A single-center analysis in Japan

We summarize herein our 14-year experience of conventional treatment outcomes before the era of molecular-targeted therapy and immunotherapy. Specifically, we conducted a retrospective review of our 252 patients with primary cutaneous melanoma (acral lentiginous melanoma [ALM], n = 121; non-acral lentiginous melanoma [non-ALM], n = 131), and compared the prognostic factors between ALM and non-ALM. Melanoma-specific survival and disease-free survival were estimated using the Kaplan-Meier method. Regarding the results, all patients were Japanese (106 male and 146 female), with a mean age of 60.1 years. Among ALM patients, age was elder and primary tumor size was larger than non-ALM. As for tumor thickness, in situ lesions were more frequently observed in ALM. There was no significant difference in the distribution of tumor thickness between the two groups when excluding the in situ lesions. For treatment of the primary melanoma, 248 patients (98.4%) had undergone curative surgical excision and 120 patients with more than 1 mm or ulcerated melanoma had undergone sentinel lymph node biopsy. Patients with systemic metastasis primarily underwent dacarbazine-based chemotherapy. The Kaplan-Meier survival curves revealed no significant difference in melanoma-specific survival and disease-free survival between those with ALM and non-ALM. The results also showed that both ALM and non-ALM, when they initially metastasize, first affect the regional lymph nodes. Incisional biopsy was not an adverse prognostic factor. These results suggest that ALM does not differ in its biological behavior from non-ALM, so we can consider ALM as being equivalent to non-ALM. The initial treatment for ALM and non-ALM can involve the same strategy.