Thin malignant melanomas (less than 1.5 mm) with metastasis: a histological study and survival analysis.

It is known that not all thin malignant melanomas have an excellent prognosis and that the specific features identifying the patients at risk of metastasis have not been fully elucidated. We have looked at thin malignant melanomas (less than 1.5 mm) in the East of Scotland that had proven metastasis and death, and compared the clinical and histological features with a similar group (less than 1.5 mm) that have had no further recurrence after a minimum of 6-year follow-up. We identified 26 patients with thin melanomas who had developed histologically proven metastasis and/or died following adequate surgical treatment of their primary lesion. When compared with the control group, factors found to be significantly different between the two groups and present in the group that did badly were (a) histological regression, (b) lesion size, (c) Clark level IV and (d) depth of the uninvolved dermis.