MOLECULAR AND IMMUNOHISTOCHEMICAL ANALYSIS OF P53 MUTATIONS IN SCRAPINGS AND TISSUE FROM PREINVASIVE AND INVASIVE BREAST-CANCER

Mutations of the p53 gene appear to be one of the most common abnormal ities in human cancer. Although many studies have been published about p53 alterations in breast cancer, data on molecular biological detect ion of p53 mutations in in situ lesions are still rare, and the implic ations for breast cancerogenesis are unclear. Tissue samples from 83 p atients with different stages of breast cancer and from 13 patients wi th benign breast lesions were screened for p53 gene mutations by polym erase chain reaction (PCR) followed by temperature-gradient gel electr ophoresis (TGGE). p53 protein accumulation was analysed by immunohisto chemistry (IHC). Samples were gained from fresh-frozen tissue, scrapin gs. or paraffin embedded tissue. Additionally, 23 pairs of primary tum ours and corresponding lymph nodes were examined. p53 gene aberrations were found in 55.7% of the infiltrating carcinomas, in 31.5% of the d uctal carcinomas in situ (DCIS) and in one atypical ductal hyperplasia . A positive correlation was seen with high-grade tumours and with com edo. There was no statistically significant relationship with respect to age, menopausal status, tumour size, hormone receptor status or lym phatic invasion. Concordance between TGGE and IHC was seen in only 63% of the cases analysed. However, with regard to p53 mutation screening by TGGE, a high significance (P = 0.0008) was seen between standard t issue extraction and our scrape preparation technique. Among 8 pairs o f primary tumours and their corresponding lymph node metastases, only 3 harbored identical p53 mutations in the same exon, while in 5 cases with mutant p53 in the primaries, no mutation was seen in the lymph no de. Our data indicate that p53 mutations are frequent in breast tumour s associated with unfavorable prognosis, including high-grade or the c omedo histotype. There is evidence that p53 gene alterations occur ear ly in breast cancerogenesis, as mutations were detected not only in in situ carcinomas but also in atypical ductal hyperplasia.