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. M ean delay before diagnosis was 1,4 years. Thirteen patients were black and 7 white. Eight patients (40%) were initially misdiagnosed as havi ng traumatic, infective or benign lesions. Four patients presented wit h recurrent local disease after inappropriate nail excision or inadequ ate nail biopsy, while 2 patients had regional nodal spread and 2 had systemic metastases. Mean Breslow depth was 5,7 mm. The histogenetic s ubtypes were acral lentiginous melanoma (12 patients) and nodular mela noma (4 patients); 4 lesions were unclassifiable. All patients underwe nt amputation of the involved digit and 12 required node dissection (t herapeutic in 11, prophylactic in 1). Five patients (25%) are alive (m ean 52 months, range 29 - 99 months); 4 are disease-free and 1 has bra in 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.