Accumulation of p53 protein in human malignant melanoma. Relationship to clinical outcome

Paraffin-embedded tissue from the primary tumours of 116 patients with malignant melanoma, and in 40 cases also from corresponding metastases, were examined for accumulation of p53 protein. The fraction of tumours with positive p53 immunostaining was 13% in the least invasive and 36% in the most invasive primary lesions and 48% in the metastases. Where comparisons could be made, both the level and pattern of p53 immunoreactivity were the same in the primary and metastatic tumours. Nine (50%) patients with p53-positive and 34 (39%) with p53-negative primaries relapsed during the first 5 years, but no difference in disease-free period was observed between the two groups. However, an overall longer survival time was observed among patients with p53-positive primaries, especially for those with tumours less invasive than 3.0 mm. Notably, all 11 patients in this group were alive 5 years after diagnosis of the disease, whereas 15 out of 70 (21%) patients with p53-negative tumours died in same period. The results show that an increased level of p53 protein does not indicate increased degree of malignancy in melanoma, but rather suggests a more favourable disease progression.