Bilateral breast cancer.

Bilateral breast cancer has a cumulative incidence of 7% to 20% in patients with primary operable breast cancer, and the majority of these lesions are metachronous. A consensus on the management of the contralateral breast has been elusive. Much of the confusion arises from the fact that there exist marked differences of opinion regarding the impact of a second primary breast cancer on the overall prognosis. The risk of developing a contralateral breast cancer is influenced by the age of the patient, the presence of in situ disease, lobular histology of this new lesion, multicentricity, exposure to certain types of ionizing irradiation, and, possibly, family history of breast cancer. Management options include observation (clinical and mammographic surveillance), contralateral biopsy, and, rarely, prophylactic mastectomy. It is hoped that trials of breast cancer prevention, employing drugs such as tamoxifen, will identify agents capable of abrogating the risk of contralateral breast cancer and improve the ultimate outcome.