[Familial breast cancer].

Japanese breast cancer families were collected and classified into the following 7 types according to the onset age and the distribution of other cancers in the family lines; early-onset type, late-onset type, familial breast-ovarian cancer type, familial breast-prostate cancer type, familial breast-thyroid cancer type, familial male and female breast cancer type and multiple primary cancer type. We have detected no p53 germ line mutations in the patients from these families. Linkage with BRCA1 was not detected in any single families. These data indicate that neither BRCA1 or p53 is a major susceptible gene in Japanese familial breast cancer. However, in the two site-specific breast cancer families, the same nonsense mutation of the BRCA1 gene was detected.