S-100 protein: a prognostic indicator in cutaneous malignant melanoma?

A series of 215 cases of cutaneous malignant melanoma referred to a single department of clinical oncology between 1940 and 1969 was studied to assess the accuracy of the Breslow thickness and the role of S-100 protein in predicting the clinical prognosis. Histological examination of these tumours showed that although the Breslow thickness correlated well with prognosis, in a significant number of cases it did not reliably forecast clinical outcome. From this series, tissue from those patients who survived disease-free for more than 10 years and those who died within a year of diagnosis was stained immunohistochemically for S-100 protein. Contrary to the findings of earlier studies, strong staining for S-100 protein was associated with improved survival (P less than 0.001). A marked increase in the incidence of cutaneous malignant melanoma was noted during the period of the study.