Prognostic significance of the histological features of malignant melanoma.

A review of 694 patients with localized cutaneous malignant melanoma (clinical stage I) revealed that three histological features of the primary lesion had no effect of their own on survival rate but derived their prognostic significance only because of their close correlation with tumour thickness. Primary lesions of superficial spreading histogenetic type, or of low mitotic activity or showing evidence of partial regression appeared to have a more favourable prognosis than lesions of nodular histogenetic type or of high mitotic activity or showing no regression. However, the former three histological features were predominant in thin lesions which had a better prognosis than thicker lesions. It was concluded that these features exerted only an indirect effect upon survival, tumour thickness being the most important prognostic determinant.