Thin melanomas with unusual aggressive behavior: a report on nine cases. Melanoma Group of French Federation of Cancer Centers.

BACKGROUND: The major factor influencing the prognosis of cutaneous malignant melanoma (MMs) is the maximum thickness of the tumor as measured by Breslow's method. However, it has been reported that thin melanomas, which should have an excellent prognosis, may have the potential to metastasize, some with an unusually rapid course. OBJECTIVE: Our purpose was to examine prognostic indicators in relation to unusually rapid aggressive behavior in patients with thin MMs (<0.76mm). METHODS: We describe nine cases of thin MM (<.76mm) that exhibited a recurrence or metastasis during a follow-up period ranging from 3 to 10 years, among computerized records of 1118 MMs treated in a multicenter epidemiologic study. The data obtained from these nine cases were compared with nonrecurring thin MM (149 cases) of the same cohort. RESULTS: The particular aggressiveness of these thin melanomas was reflected by the short disease-free interval (3 years or less) in all ine patients. The recurring thin MM more frequently involved head and neck sites, occurred in male patients, and showed Clark's level III and IV. CONCLUSION: Our review suggests that the head and neck area is particularly involved by unusually rapidly recurring thin MM. Possible explanations are the specific problems of surgical management and the greater sun exposure of this location.