p53 protein expression in non-neoplastic lesions and benign and malignant neoplasms of soft tissue.

Alterations of the p53 tumour suppressor gene, with consequent nuclear p53 protein accumulation, are among the most common genetic lesions in human neoplasms. In the present paper we show p53 immunoreactivity in 65% of malignant and 21% of intermediate malignancy soft tissue tumours, and in 48% of benign/reactive soft tissue lesions. p53 immunoreactivity of sarcomas can be interpreted as an indirect indication of a mutation of the corresponding p53 gene, suggesting that its alteration may have a role in their pathogenesis. Our data on p53 immunoreactivity in benign lesions of the soft tissues are among the first demonstrations of p53 over-expression in benign/reactive conditions. We cannot exclude mutations of the p53 gene in these cases, but it is difficult to sustain this hypothesis in reactive/pseudoneoplastic lesions. Alternatively p53 immunoreactivity in benign processes could be due to an increase in wild-type p53 as a result of different physiological mechanisms (cell type-specific p53 regulation, cell maturation, DNA repair). Our results do not indicate that immunohistochemical demonstration of p53 expression is a marker of malignancy in soft tissue tumours and therefore is of limited use in differential diagnosis. However, they suggest the need for further molecular genetic studies in order to elucidate the biological significance of the abnormal expression of p53 in benign soft tissue lesions.