Breast cancer is a disease in which malignant (cancerous) cells form in the breast tissue.
The breast gland is made up of lobules and ducts. Each breast has 15 to 20 lobes, and each lobe is divided into several lobules. The lobules end in a number of milk-producing vesicles. The lobes, lobules, and follicles are connected by thin ducts called ducts.
Anatomy of the female breast showing the lymph nodes, nipple, areola, chest wall, ribs, muscle, fatty tissue, lobe, ducts, and lobules. The nipple and areola are shown on the outside of the breast. The figure also shows the lymph nodes, lobes, lobules, ducts, and other parts of the interior of the breast.
There are also blood vessels and lymphatic vessels within the breast. The lymphatic vessels carry an almost colorless, watery fluid called lymph. The lymphatic vessels carry lymph between the lymph nodes. Lymph nodes are very small, bean-like structures that filter lymph and store the white blood cells used to help fight infection and disease. Clusters of lymph nodes are usually concentrated in the armpit (under the arm), above the collarbone, and in the chest near the breast.
For more information about breast cancer, see the following PDQ summary:
Breast cancer is the second leading cause of cancer death among women in the United States. Breast cancer is the fifth leading cause of cancer death in Chinese women.
U.S. women have more breast cancer than any other type of cancer except skin cancer.
The risk of breast cancer usually increases with a woman’s age. White women are more likely to develop breast cancer than black women, but black women have a higher chance of dying from breast cancer than white women.
Men rarely develop breast cancer. Because men who develop breast cancer usually have a visible lump, screening is not very meaningful.
Different influences can increase or decrease the risk of developing breast cancer.
For more information about risk and protective factors for breast cancer, see the PDQ summary in Breast Cancer Prevention.