Regression in malignant melanoma. A histologic feature without independent prognostic significance.

A total of 844 cutaneous malignant melanomas were examined prospectively for the presence or absence of histologic regression within the primary tumor. Cases were then stratified into three groups according to tumor thickness and survival was compared between substrata with and without regression in each group. The distribution of other major prognostic variables within these substrata was assessed and their influence as potential confounding variables considered. No statistically significant effect of regression on survival was found in any of the three thickness strata. These results do not confirm the finding of an earlier study, which suggested that regression may be a poor prognostic sign when found in association with thin malignant melanomas. Regression was almost invariably associated with the radial growth phase of melanomas. Regression was more common in male than in female patients, and was more frequent in association with truncal than extremity or head and neck melanomas.