The term “bilateral” in medicine signifies that a condition affects both sides of the body. When applied to the breasts, it refers to any process, diagnosis, or surgical procedure involving both the left and right breast. This designation is used to describe a wide range of situations, from benign changes to the presence of cancer in both breasts. The concept of bilaterality is important in breast health for both diagnostic and treatment-related decisions.
Common Bilateral Breast Conditions
When cancer is found in both breasts, it is referred to as bilateral breast cancer, a condition that occurs in about 3% of breast cancer patients in the U.S. It is classified into two main types based on timing. Synchronous bilateral breast cancer is when tumors are discovered in both breasts simultaneously or within a short period, typically three to twelve months. In contrast, metachronous bilateral breast cancer occurs when a second primary cancer develops in the opposite breast at a later time, usually at least one year after the initial diagnosis.
Compared to unilateral cancer, individuals with bilateral disease are often younger at the time of diagnosis and may have tumors that are smaller and at an earlier stage. The most common sign of cancer in one or both breasts is a painless lump. Other symptoms can include swelling, skin dimpling, nipple retraction, or discharge other than breast milk. It is possible to have cancer in both breasts even if a lump is only felt in one.
Not all conditions affecting both breasts are cancerous. Benign (non-cancerous) changes are common and can occur in both breasts. Fibrocystic change is a frequent benign condition that causes breasts to feel lumpy, tender, and painful, often in sync with the menstrual cycle. These symptoms are caused by breast tissue overreacting to hormonal fluctuations. Breast cysts, which are fluid-filled sacs, can also develop in both breasts as women age.
Diagnostic Imaging of Both Breasts
When a breast concern arises, even if it is only on one side, standard medical practice involves imaging both breasts. The primary tools used for this are mammography, breast ultrasound, and magnetic resonance imaging (MRI). A bilateral mammogram, which is an X-ray of both breasts, is the most common screening tool.
The reason for imaging the contralateral (opposite) breast is to screen for hidden abnormalities that have not yet produced symptoms. A second reason is to establish a healthy baseline image of the other breast. This baseline serves as a valuable comparison tool for future imaging, helping to more easily identify subtle changes over time.
For certain individuals, like younger women with dense breast tissue, an ultrasound may be used with or instead of a mammogram. Dense breast tissue can sometimes obscure small tumors on a mammogram, and ultrasound provides a clearer view in these cases. A breast MRI is a more sensitive test that may be recommended for individuals at high risk for breast cancer or to get a more detailed look at an abnormality.
Surgical Procedures Involving Both Breasts
Surgical interventions can involve both breasts for either treatment or prevention. A bilateral mastectomy is the surgical removal of both breasts. A therapeutic bilateral mastectomy is performed to treat cancer that has been diagnosed in both breasts, either at the same time or at different times.
Conversely, a prophylactic or risk-reducing bilateral mastectomy is the removal of both breasts to lower the future risk of developing cancer. This preventative surgery is for individuals who have a significantly elevated lifetime risk. This surgery can lower the risk of breast cancer by 90% or more in high-risk individuals. Following a bilateral mastectomy, patients have several options for breast reconstruction.
Bilateral breast reconstruction aims to restore the shape and appearance of the breasts. This can be achieved using implants, which are silicone or saline devices placed under the skin or chest muscle. Another option is autologous tissue flap reconstruction, which uses a patient’s own tissue, like skin and fat from the abdomen or back, to create new breast mounds.
A bilateral lumpectomy, also known as breast-conserving surgery, is another surgical option. In this procedure, only the cancerous tumor and a small margin of surrounding healthy tissue are removed from each breast. This is often followed by radiation therapy to destroy any remaining cancer cells. The choice between a mastectomy and a lumpectomy depends on factors like tumor size, patient health, and personal preference.
Risk Factors and Genetic Considerations
Genetic predisposition can increase an individual’s likelihood of developing disease in both breasts or influence the decision to pursue preventative surgery. Inherited mutations in specific genes, most notably BRCA1 and BRCA2, are associated with a higher lifetime risk of developing breast, ovarian, and other cancers.
Individuals carrying a harmful mutation in the BRCA1 or BRCA2 gene have a greater chance of being diagnosed with bilateral breast cancer compared to the general population. These genes normally produce proteins that help repair damaged DNA and suppress tumor growth. When they are mutated and do not function correctly, it can lead to the development of cancer.
A family history of breast or ovarian cancer is another consideration, even in the absence of a known genetic mutation. Having multiple first-degree relatives (mother, sister, or daughter) diagnosed with breast cancer elevates a person’s risk. This is especially true if the diagnoses occurred at a young age.