P53 PROTEIN EXPRESSION AND NUCLEAR-DNA CONTENT IN BREAST INTRADUCTAL PROLIFERATIONS

Immunohistochemical analysis of the p53 gene protein and cytometric as sessment of nuclear DNA were performed in a series of 51 cases of intr aductal breast proliferation. The series included 22 cases of intraduc tal hyperplasia without atypia, 6 cases of intraductal hyperplasia wit h atypia, and 23 cases of pure intraductal carcinoma. Expression of p5 3 protein was detected in one case of intraductal hyperplasia without atypia (4.5 per cent), one case of intraductal hyperplasia with atypia (16.6 per cent) and six cases of intraductal carcinoma (26.0 per cent ). No significant correlation was observed between p53 expression and histological subtype of intraductal carcinoma. Aneuploidy was demonstr ated in two cases of intraductal hyperplasia with atypia (33.3 per cen t) and in 18 cases of intraductal carcinoma (78.2 per cent). All cases of intraductal hyperplasia without atypia were euploid. No significan t association was observed between p53 protein expression and ploidy i n intraductal hyperplasia. The only case of intraductal hyperplasia wi thout atypia positive for p53 was euploid, whereas the only p53-positi ve case of intraductal hyperplasia with atypia was aneuploid. Among th e intraductal carcinomas, only the aneuploid cases showed positivity f or p53, regardless of histological subtype. The results suggest that s ome of the changes observed in invasive breast carcinoma, such as p53 expression and aneuploidy, are already present in breast intraductal p roliferation, especially in areas with atypia and in intraductal carci noma. The expression of p53 in breast intraductal proliferation may re flect the acquisition of p53 gene mutations in cells unable adequately to repair DNA damage, with genomic instability which would lead to cl onal expansion and putative evolution to invasive disease.