The thin malignant melanoma: changing patterns of epidemiology and treatment.

In the past few years a change has been noticed in the behavior of cutaneous malignant melanoma, with higher cure and survival rates. A retrospective review of all cases of primary cutaneous malignant melanoma during the years 1970-1979 in Chaim Sheba Medical Center reveals a possible explanation for this. The microscopic findings were reevaluated, diagnosis confirmed, and thickness of the tumor measured in millimeters. The number of cases diagnosed rose from eight in 1970 to 45 in 1979. A constant rise in number of thin melanomas (less than 0.75 mm in depth) was noticed. The percentage of thin melanoma rose from 11.1% of all melanomas in 1970 to 57.7% in 1979. Greater public and medical awareness of the danger of pigmented cutaneous lesions has probably triggered an earlier diagnosis of melanoma. Each suspected lesion is completely excised with a 1-cm free margin. No further excision is undertaken if a thin melanoma is diagnosed (excluding the more malignant regressing melanoma) on frozen section. Of the patients seen in 1979, 57% were spared wide excision and general anesthesia.