Nail apparatus melanoma in a Japanese population: a comparative study of surgical procedures and prognoses in a large series of 151 cases

Nail apparatus melanoma (NAM) is a rare subtype of malignant melanoma with a prevalence that varies among populations. Conservative surgical approaches for thin to intermediate NAMs have recently been reported, however, their adoption is controversial, and resulting long-term prognoses are unknown. The purpose of this study was to determine the prognosis of NAM in a sample Asian population, and to investigate whether there is a difference in the local control and overall survival (OS) rates according to the extent of resection of the primary tumour. We performed a retrospective study of NAM patients treated at five medical institutions in Japan between 2000 and 2013. Outcomes according to surgery (amputation vs. resection) and tumour thickness were compared. We identified 151 cases of NAM in 83 men and 68 women; the thumb (n = 50; 33.1%) and hallux (n = 55; 36.4%) were the most common sites. No local recurrence was detected following any of the surgical procedures; Kaplan-Meier survival analysis revealed that the surgical procedure type was not significantly associated with disease-free survival (p = 0.786) or OS (p = 0.997). Five-year OS rates according to tumour thickness were 100% for in situ, 94.4% for ≤1-mm, 91.7% for 1.01-2.0-mm, 72.7% for 2.01-4.0-mm, and 47.6% for ≥4.01-mm tumours. Surgical procedure type does not influence survival as long as total primary tumour resection is accomplished. The prognosis of NAM is comparable to that of other types of melanoma.