Genetic study of breast cancer: Identification of a high risk group

A group of women was identified whose risk for breast cancer was 47-to 51-fold higher than that experienced by control women. These high-risk women were sisters of patients whose mothers had breast cancer. The disease in these families developed premenopausally, often bilaterally, and was seemingly associated with ovarian function. Since disease susceptibility was transmitted from an affected mother to approximately 30% of her daughters, this early, bilateral form of breast cancer appeared to be strongly heritable. Another, less heritable form was identified in families comprised of at least two affected sisters and unaffected mothers. The risk in these families was 3-fold higher than that of controls, and the disease was primarily postmenopausal, unilateral, and was not strongly associated with ovarian function. No difference was observed in the transmission of breast cancer through paternal and maternal lines of descent.