Subungual melanoma.

Twenty (1.5%) of 1,350 patients with malignant melanoma treated during a 17-year period had their primary lesion in the nail bed. The thumb (5 patients) and big toe (7) were the most commonly involved digits. Mean delay before diagnosis was 1.4 years. Thirteen patients were black and 7 white. Eight patients (40%) were initially misdiagnosed as having traumatic, infective or benign lesions. Four patients presented with recurrent local disease after inappropriate nail excision or inadequate nail biopsy, while 2 patients had regional nodal spread and 2 had systemic metastases. Mean Breslow depth was 5.7 mm. The histogenetic subtypes were acral lentiginous melanoma (12 patients) and nodular melanoma (4 patients); 4 lesions were unclassifiable. All patients underwent amputation of the involved digit and 12 required node dissection (therapeutic in 11, prophylactic in 1). Five patients (25%) are alive (mean 52 months, range 29-99 months); 4 are disease-free and 1 has brain metastases. Overall median survival was 32 months with a 26% 5-year survival rate. Delayed diagnosis and advanced disease at presentation contributed to the poor prognosis in nail bed melanoma.