A woman’s breast is made of glandular tissue, connective tissue, fatty tissue, blood vessels, lymph tissue, and nerves. Each breast contains up to 20 sections of glandular tissue called lobes. Each lobe has many smaller sections called lobules, where milk is made. Milk flows from the lobules through thin tubes called ducts to the nipple. The nipple is the small, raised area at the tip of the breast. The areola is the area of darker-colored skin around the nipple.
Each breast also contains lymph vessels. These are thin tubes that carry lymph to small, bean-shaped glands called lymph nodes. Lymph nodes are found near the breast, under the arm, and throughout the body. Lymph nodes and lymph vessels are part of the lymph system, which helps your body fight disease and infection. The chest muscle and chest wall are behind the breasts.
Cancer is a disease in which cells become abnormal and form more cells in an uncontrolled way. With breast cancer, the cancer begins in the tissues that make up the breasts. The cancer cells may form a mass called a tumor. (Note: Not all tumors are cancer.) They may also invade nearby tissue and spread to lymph nodes and other parts of the body. The most common types of breast cancer are:
Ductal carcinoma – Cancer that begins in the ducts and grows into surrounding tissues. About 8 in 10 breast cancers are this type.
Lobular carcinoma (LAH-byuh-luhr KAR-sih-NOH-muh) – Cancer that begins in lobules and grows into surrounding tissues. About 1 in 10 breast cancers are this type.
With routine screening, breast cancer often can be found at an early stage, before the cancer has spread.
For more information visit: http://www.womenshealth.gov/breast-cancer/what-is-breast-cancer/index.html