Breast

Breast refers to the pair of mammary glands located on the anterior chest wall. In humans, breast tissue occurs in both sexes but is typically larger and functionally active in females, where it is specialized for lactation. The breast consists of glandular tissue arranged into lobes and lobules, a supporting stroma of connective tissue and fat, and a skin-covered surface.

The glandular tissue lies mostly beneath the nipple and areola. From each lobule, ducts converge toward the nipple to form lactiferous ducts that open at the nipple. The nipple projects from the center of the pigmented areola, which contains sebaceous Montgomery glands that lubricate the area.

Blood supply is primarily via the internal thoracic (mammary) arteries and perforating branches of the lateral thoracic artery. Venous drainage follows a parallel pattern to the veins, draining into the internal thoracic and axillary veins. Sensory innervation of the nipple-areolar complex chiefly involves the anterior branches of the intercostal nerves.

Lymphatic drainage is mainly to axillary lymph nodes, with additional drainage to parasternal nodes along the internal thoracic vessels. The lymphatic pattern is clinically important for understanding the spread of breast cancer.

Developmentally, breast tissue changes with puberty under estrogen influence, with ductal growth and lobular formation. During pregnancy hormonal changes promote further development of milk-producing units, and lactation occurs after birth in response to prolactin and oxytocin. Fat content influences breast size and appearance and varies with body adiposity and age.

Clinical considerations include breast cancer, which is one of the most common cancers worldwide, with screening programs using mammography and imaging. Benign conditions such as fibrocystic changes, mastitis, and gynecomastia can cause symptoms but are not malignant.