Next Page Chapter 1. The normal, mature female breast varies from approximately 50 to 500 grams, and is largely influenced by the body habitus of the individual, with a large variation in the fat content of the breast. There is extension of the breast tissue into the axilla to a variable degree as well. The normal breast is composed of roughly 15 to 25 lobes, each of which has its own major duct opening into the lactiferous sinus, just below the nipple. Lobules are composed of multiple glandular units enveloped by a loose stroma and are demarcated by a basement membrane.
Adipose tissue is distributed within and around the lobes of breast parenchymal tissue.
The overlying nipple is composed of dense connective tissue with the confluence of each of the major ducts from the breast lobes, which coalesce into the lactiferous sinus and lactiferous ducts. The skin of the nipple contains multiple sebaceous glands and is variably pigmented, as is the surrounding areola, which contains bundles of smooth muscle cells and small milk ducts. The breast tissue lies superficial to the muscle of the chest, and is drained by lymph nodes to multiple sites, including the skin around the breast, the chest wall, and the axilla. The axilla constitutes a large majority of the lymphatic drainage from the breast. Thus, the tissue of axillary lymph node involvement by breast cancer is important in assessing the status of metastatic spread of the disease, and for appropriate surgical, medical, and radiation therapy.