Prophylactic mastectomy (PM) is not a procedure, per se; it is defined as the removal of the breast in the absence of malignant disease to reduce the risk of breast cancer occurrence. PM is also known as preventive mastectomy and is typically bilateral. PM may be performed unilaterally in a patient who has previously undergone a mastectomy in the opposite breast for an invasive cancer and is at risk for developing cancer in the remaining breast.
There are several PM procedures, which are distinguished by the amount of breast tissue and other tissues that are removed. These procedures include:
- Simple mastectomy (SM) [also known as total mastectomy (TM)]: The entire breast is removed, including all the breast tissue, nipple-areola complex, and a small portion of the overlying skin, preserving muscle, fascia, and axillary lymph nodes.
- Skin-sparing mastectomy (SSM): A small (keyhole) incision, circling the areola, is made. Even though the opening is smaller, the same amount of breast tissue is removed. The areola complex cannot be preserved as the breast ductal system travels through this complex. Scarring is negligible and 90% of the skin is preserved. Reconstruction is performed at the same time, using tissue from the patient’s abdomen or latissimus dorsi (back) muscles.
- Subcutaneous mastectomy (SCM): The tumor and breast tissue are removed, sparing the skin, lymphatic drainage system, and nipple-areola complex. The breast can be reconstructed by creating a submuscular or subcutaneous pocket for an implant. The reconstruction may be easier, but if SCM is done for cancer, some cancer cells may remain undetected.
PMs may be considered in women thought to be at high-risk of developing breast cancer, either do to:
- A family history,
- The presence of genetic mutations such as BRCA1 or BRCA2 mutation,
- Having received radiation therapy to the chest, or
- The presence of lesions associated with an increased cancer risk such as atypical hyperplasia (abnormal increase of normal cells within a tissue or organ) and lobular carcinoma in situ (LCIS).
LCIS is both a risk factor for all types of cancer, including bilateral cancer, and in some cases, a precursor for invasive lobular cancer. For those who develop invasive cancer, up to 35% may have bilateral cancer. Therefore, bilateral PM may be performed to eliminate the risk of cancer arising elsewhere; chemoprevention and close surveillance are alternative risk reduction strategies. PMs are typically bilateral but can also describe a unilateral mastectomy in a patient who has previously undergone or is currently undergoing a mastectomy in the opposite breast for an invasive cancer.
The appropriateness of a PM is a complicated risk-benefit analysis that requires estimates of a patient’s risk of breast cancer, typically based on the patient’s family history of breast cancer and other factors. Several models are available to assess risk, such as the Claus model and the Gail model. Breast cancer history in first- and second-degree relatives is used to estimate breast cancer risk in the Claus model. The Gail model uses the following 5 risk factors: age at evaluation, age at menarche, age at first live birth, number of breast biopsies, and number of first-degree relatives with breast cancer.
Candidates for PM may have undergone or may undergo counseling regarding cancer risk from a provider skilled in assessing cancer risk other that the surgeon or oncologist, in addition to various treatment options, surveillance, or chemoprevention.