A breast is made up of three main parts: glands, ducts, and connective tissue. The glands produce milk. The ducts are passages that carry milk to the nipple. The connective tissue (which consists of fibrous and fatty tissue) connects and holds everything together.
No breast is typical. What is normal for you may not be normal for another woman. Most women say their breasts feel lumpy or uneven. The way your breasts look and feel can be affected by getting your period, having children, losing or gaining weight, and taking certain medications. Breasts also tend to change as you age.
Many conditions can cause lumps in the breast, including cancer. But most breast lumps are caused by other medical conditions. The two most common causes of breast lumps are fibrocystic breast condition and cysts. Fibrocystic condition causes noncancerous changes in the breast that can make them lumpy, tender, and sore. Cysts are small fluid-filled sacs that can develop in the breast.
Sometimes breast cells become abnormal. These abnormal cells grow, divide, and create new cells that the body does not need and that do not function normally. The extra cells form a mass called a tumor. Some tumors are "benign" or not cancer. These tumors usually stay in one spot in the breast and do not cause big health problems. Other tumors are "malignant" and are cancer. Breast cancer often starts out too small to be felt. As it grows, it can spread throughout the breast or to other parts of the body. This causes serious health problems and can cause death.
There are different kinds of breast cancer. The kind of breast cancer depends on which cells in the breast turn into cancer. Breast cancer can begin in different parts of the breast, like the ducts or the lobes.
Common kinds of breast cancer are—
There are several other less common kinds of breast cancer, such as Paget's disease or inflammatory breast cancer. For more information, visit the National Cancer Institute's Inflammatory Breast Cancer and Paget Disease of the Nipple: Questions and Answers.
Page last reviewed: August 31, 2010
Page last updated: June 9, 2011
Content source: Division of Cancer Prevention and Control, National Center for Chronic Disease Prevention and Health Promotion