The breasts are hormonally-responsive organs that facilitate lactation and breastfeeding. Each breast contains extensively branched glandular tissue made up of lobules and ducts, which produce milk and carry milk to the nipple. The glandular tissue is surrounded by fat cells, blood and lymph vessels, lymph nodes and nerve tissue. Breast swelling may develop as a result of normal physiological changes within the body, or as a result of a severe underlying disorder.
Hormone Changes
One natural cause of breast swelling is the natural fluctuation of hormones that occurs during the menstrual cycle and during pregnancy. Female hormones, especially estrogen, bind to chemical receptors on breast cells and trigger cellular proliferation. As a result, an increase in estrogen production leads to an increase in breast growth, which may present as slight swelling. Breast swelling as a result of hormone changes may cause some discomfort and tenderness, which may be coupled with changes in breast texture. Swelling typically occurs before the onset of menstruation, and during the first stages of pregnancy as the breasts grow in preparation for lactation.
Breast Infection
Another possible cause of swelling is a breast infection, also called mastitis. Breast infections develop when bacteria enter the breasts through cracks or cuts in the skin and colonize within the fat or glandular tissue. They commonly occur during breastfeeding, since infant suckling can cause small lesions on the nipples. In response to bacterial colonization, the immune system begins to attack the foreign bacteria, leading to breast swelling and inflammation. Mastitis most commonly results from infection by the bacterium Staphylococcus aureus, reports the University of Maryland Medical Center. Mastitis treatment generally includes antibiotics to help clear the infection, as well as over-the-counter analgesic medication to ease pain and discomfort.
Inflammatory Breast Cancer
Another possible cause of breast swelling is inflammatory breast cancer, a rare form of cancer that accounts for up to five percent of breast cancer diagnoses. Inflammatory breast cancer develops when mutant breast cells begin to proliferate out of control and begin to block the lymphatic vessels. Since these vessels normally facilitate circulation of lymphatic fluid into and out of the breast, blocking these ducts leads to fluid buildup in the breast leading to swelling. Patients with inflammatory breast cancer experience swelling in one breast accompanied by red and inflamed skin over the breast, inverted nipples and a burning sensation, according to the National Cancer Institute.
