Recurrence potential of thin primary melanomas.

Between April 1971 and January 1985, the University of California at Los Angeles (UCLA) Division of Surgical Oncology has seen 649 patients diagnosed with thin primary melanomas, as defined by a Clark level less than IV and Breslow depth less than 0.76 mm. Thirty-six patients, whose primary diagnosis was confirmed by UCLA pathologists, presented with or subsequently developed melanoma metastases. Twenty-four (67%) had Clark level II lesions, whereas the remaining 12 (33%) had Clark level III lesions. Metastases were noted more frequently in men than in women, with a man-to-woman ratio of 3 to 2. The site of the primary lesion in this group was most frequently on the trunk (16 of 36 cases, 44%), followed by the head and neck (9 of 36 cases, 25%) and arm and shoulder (7 of 36 cases, 19%). Metastasizing thin lesions were least likely to occur on the leg and hip (4 of 36 cases, 11%). Twenty of these lesions were recently reexamined, and 17 of 20 cases (85%) demonstrated evidence of regression. Twenty-eight patients (78%) had their first metastases to regional lymph nodes. Fifteen remained alive with no evidence of disease at a median follow-up of 99 months. Twenty patients died from systemic metastases, and one patient was alive with brain metastasis at the time of this article. Although infrequent, metastases from thin melanomas do occur, suggesting the need for careful long-term follow-up and immediate investigation of adenopathy even in low-risk patients.