Breasts undergo cycles of proliferation and development throughout a women's fertile life. Bilateral breast soreness, tenderness affecting both breasts, is normal during periods of breast growth, during pregnancy and during some parts of the menstrual cycle. Unilateral breast pain--pain in one breast--can indicate a potentially harmful underlying condition that requires medical attention.
Breast Infection
One possible cause of pain in one breast is the development of a breast infection, a condition called mastitis. Mastitis occurs when the skin of the breast becomes cracked, allowing bacterial, viral or fungal microbes to enter into the breast tissue and infect the fat of the breasts. The infection leads to swelling and inflammation that press against the other tissues of the breast, causing irritation and pain. The University of Maryland Medical Center indicates that the majority of breast infections are caused by bacteria, and a course of antibiotic therapy will usually clear up the infection. Over-the-counter painkillers can help control pain and inflammation.
Sclerosing Adenosis
Sclerosing adenosis can cause pain and tenderness in one breast. Sclerosing adenosis is a benign breast condition that stems from abnormal growth of the breast lobules--the glands that produce and secrete milk. Patients with sclerosing adenosis develop small growths of calcifications that can sometimes develop into lumps, reports the Ohio State University Medical Center. As the lumps push on surrounding breast tissue, the breast becomes sore and tender to the touch. Sclerosing adenosis can be detected on a mammogram or during a physical examination, if a lump is present, then confirmed with a tissue biopsy to rule out the possibility of breast cancer. Surgery to remove the growths can alleviate breast pain.
Inflammatory Breast Cancer
Another possible cause of pain in one breast is inflammatory breast cancer, also called IBC. IBC is a relatively rare form of cancer that develops when abnormal cell growth blocks normal lymph fluid circulation in the breast, leading to the development of a warm, enlarged, inflamed and painful breast. Patients with IBC also experience skin abnormalities such as wrinkling or dimpling and may experience skin irritation as the cancer spreads to the skin. IBC is a relatively rare form of breast cancer which accounts for 1 to 5 percent of breast cancer diagnoses in the United States, reports the National Cancer Institute. It can be diagnosed by tissue biopsy and requires aggressive cancer treatment to slow or stop cancer growth.
