Breast cancer and pregnancy.

This article addresses a challenging diagnostic and treatment dilemma encountered in the care of pregnant women-breast cancer. The treatment of a breast cancer is significantly affected by an ongoing pregnancy and may result in an increased risk for a poor outcome in the mother. The definition, incidence, mechanism, diagnosis, and treatment of breast cancer associated with pregnancy and the normal physiologic and endocrine changes in the breast during pregnancy that contribute to the difficulty encountered by practitioners in diagnosing and treating the disorder are reviewed. The risks associated with pregnancy after breast cancer treatment and the effect of pregnancy on lifetime risk for breast cancer in the general population and for women with mutations in BRCA1 and BRCA2 are also discussed.