Nevertheless, breast cancers carrying BRCA1 mutations have come to be associated with a particular pathology, referred to as medullary carcinoma, even though only 13% of BRCA1-associated tumors have a clinically recognized medullary or atypical medullary pathology (Breast Cancer Linkage Consortium, 1997, Lakhani et al., 1998). This evidence concerns the gene BRCA1 and breast cancer.