Breast Cancer Health Center

Breast Cancer and Preventive Mastectomy

In hopes of avoiding future disease, some women at very high risk of developing breast cancer elect to have both breasts surgically removed, a procedure called bilateral prophylactic mastectomy or preventive mastectomy. The surgery aims to remove all breast tissue that potentially could develop breast cancer. 

Preventive breast cancer surgery also may be considered if a woman has already had breast cancer and is therefore at increased risk for developing the disease again in either breast. A preventive mastectomy might also be considered if the woman has the BRCA1 or BRCA2 genetic mutation that increases risk of breast cancer, a strong family history of breast cancer, or atypical lobular hyperplasia or lobular carcinoma in situ (LCIS). Atypical lobular hyperplasia is a condition in which there are irregular cells lining the milk lobes; lobular carcinoma in situ is a noninvasive breast cancer.

Can a Prophylactic Mastectomy Prevent Breast Cancer?

A recent study suggests that prophylactic mastectomy may reduce the risk of breast cancer by up to 100% if there is a strong family history of breast cancer or a BRCA genetic mutation. However, risk reduction results vary widely for many reasons. In some studies, women had prophylactic mastectomies for  non-high risk reasons,such as pain, fibrocystic breast disease, dense breast tissue, cancer phobia, or a family history of breast cancer.

 Approximately 10% of women will develop breast cancer, even though their breast tissue has been removed. But in most studies, patients did not develop breast cancer after prophylactic mastectomy. However, many of these patients would not have been considered high risk for developing cancer.

Some experts have argued that even for high-risk women, prophylactic mastectomy is inappropriate, because not all breast tissue can be removed during a surgical procedure. In addition, the only group undergoing prophylactic mastectomy that had a survival advantage (lived longer) were pre-menopausal women, with endocrine receptor-negative breast cancers. To understand why, we need to know what comprises breast tissue and where cancer originates.

Where Does Breast Cancer Form?

Breast cancers may develop in the glandular tissue of the breast, specifically in the milk ducts and the milk lobules. These ducts and lobules are located in all parts of the breast tissue, including tissue just under the skin. The breast tissue extends from the collarbone to the lower rib margin, and from the middle of the chest, around the side and under the arm.

In a mastectomy, it is necessary to remove tissue from just beneath the skin down to the chest wall and around the borders of the chest. However, even with very thorough and delicate surgical techniques, it is impossible to remove every milk duct and lobule, given the extent of the breast tissue and the location of these glands beneath the skin.