p53 immunoreactivity in human malignant melanoma and dysplastic naevi.

Expression of the tumour suppressor protein, p53, was determined in 77 cutaneous melanocytic lesions, and in five lymph node metastases from malignant melanoma, in an immunohistochemical study employing CM-1, an antiserum raised against recombinant human p53 protein. Because wild-type p53 protein is rapidly degraded in normal cells, p53 immunoreactivity suggests the presence of an abnormally stable p53 protein. This may occur through either post-translational mechanisms or gene mutation. A highly significant correlation was found between p53 immunoreactivity and malignancy in melanocytic lesions (P < 0.0001). Overall, p53 immunoreactivity was observed in 63% of tumour specimens examined, but not in benign melanocytic naevi, although occasional foci of weak nuclear p53 immunoreactivity were observed in a minority of dysplastic naevi and a solitary Spitz naevus. A significant correlation was also found between strong p53 immunoreactivity and malignant melanomas associated with a poor prognosis (P = 0.008). These data suggest an important role for p53 tumour suppressor protein in the biology of human cutaneous malignant melanoma.