Breast Cancer

Breast cancer is the most common cancer diagnosed in women and the second most common cause of death from cancer among women worldwide. The breasts are paired glands of variable size and density that lie superficial to the pectoralis major muscle. They contain milk-producing cells arranged in lobules; multiple lobules are aggregated into lobes with interspersed fat. Milk and other secretions are produced in acini and extruded through lactiferous ducts that exit at the nipple. Breasts are anchored to the underlying muscular fascia by Cooper ligaments, which support the breast.

Breast cancer most commonly arises in the ductal epithelium (ie, ductal carcinoma) but can also develop in the breast lobules (ie, lobular carcinoma). Several risk factors for breast cancer have been well described. In Western countries, screening programs have succeeded in identifying most breast cancers through screening rather than due to symptoms. However, in much of the developing world, a breast mass or abnormal nipple discharge is often the presenting symptom. Breast cancer is diagnosed through physical examination, breast imaging, and tissue biopsy. Treatment options include surgery, chemotherapy, radiation, hormonal therapy, and, more recently, immunotherapy. Factors such as histology, stage, tumor markers, and genetic abnormalities guide individualized treatment decisions.