Pre-cancerous breast lesions: implications for breast cancer prevention trials

The relationship between benign breast disease and breast cancer has become the focus of increased clinical attention as breast cancer prevention becomes a clinical reality. In this setting an understanding of the magnitude of the increase in risk conferred by the various types of benign breast disease assumes increasing importance. When benign breast disease is considered as an aggregate, estimates of the relative risk of breast cancer development range from 0.8 to 4.5. This article describes the risk associated with proliferative and non-proliferative benign breast disease, as well as the rationale for considering lobular carcinoma in situ and ductal carcinoma in situ (in some cases) as risk factors for breast carcinoma rather than actual malignant lesions. Mathematical models can provide a more precise estimate of breast cancer risk, but these efforts may be confounded by the lack of uniformity in the pathologic definition of borderline benign breast lesions. The breast cancer prevention trials offer a unique opportunity to improve our database on the natural history of high risk benign breast lesions, while attempting to reduce the 44,000 deaths occurring annually from breast cancer.