Approximately 2% to 5% of all breast cancers are hereditary, meaning that the cancer predisposition is carried as a monogenic trait. Several highly penetrant breast cancer predisposing genes have been identified. These discoveries will permit a refined description of breast cancer occurring as part of the different genetic syndromes. We reviewed the medical literature on the clinico-pathological features of breast cancer associated with the major breast cancer susceptibility genes BRCA1 and BRCA2. BRCA1-associated breast cancers are more frequently ductal invasive, high-grade carcinomas with an important lymphocytic infiltration. They are aneuploid, estrogen and progesterone receptors negative, and p53 positive. BRCA2-related breast cancers tend to be higher-grade tumors than are non-hereditary cases, although this association is less strong then for BRCA1 cases. These tumors exhibit substantially less tubule formation, but mitotic count and cellular pleomorphism do not differ significantly from those of sporadic cases. The overall pattern of the identified pathological characteristics suggests a carcinogenic pathway in BRCA1- and BRCA2-related breast cancers different from that found in sporadic cases. The probability of finding a BRCA1/2 germ-line mutation is partly determined by these characteristics. In addition, these features will likely influence the behavior of BRCA1/2-related breast cancer.
Copyright 2000 Wiley-Liss, Inc.