Cancers are a group of diseases that cause cells in the body to change and grow out of control. Most types of cancer cells form a lump or mass called a tumor, and are named after the part of the body where the tumor first starts.


Breast cancer begins in breast tissue, which is made up of glands called lobules that produce milk, and the ducts that connect lobules to the nipple. The remainder of the breast is made up of fatty, connective, and lymphatic tissue.


Most types of tumors that form in the breast are benign; that is, they are not cancer at all. Benign breast tumors are abnormal growths, but they do not grow and spread like cancer does, and are not life-threatening.


Some breast tumors are cancerous, but are called in situ, because they have not spread beyond the area where they began. In situ breast cancers are confined within the ducts (ductal carcinoma in situ) or lobules (lobular carcinoma in situ) of the breast, and nearly all cancers at this stage can be cured. Some oncologists believe that lobular carcinoma in situ is not a true cancer but is a marker of increased risk for developing invasive cancer in the future.


Other cancerous breast tumors are invasive, or infiltrating. These cancers start in the ducts or lobules of the breast but have begun breaking through the duct or gland walls to invade the surrounding fatty tissue of the breast. The seriousness of invasive breast cancer is strongly influenced by the stage of the disease, or how far the cancer has spread, when it is first diagnosed:


  • local stage describes cancers confined to the breast;

  • regional stage tumors have spread to surrounding tissue, or nearby lymph nodes;

  • distant stage cancers have metastasized (spread to distant sites).

Source: American Cancer Society, Inc.

The most common sign of breast cancer is a new lump or mass. A mass that is painless, hard, and has irregular edges is more likely to be cancerous, but some rare cancers are tender, soft, and rounded.


Other Symptoms


A generalized swelling of part of a breast (even if no distinct lump is felt).


Breast skin irritation or dimpling.


Nipple pain or retraction (turning inward), redness or scaliness of the nipple or breast skin.


Discharge other than breast milk.


Many of these symptoms can also be due to benign breast conditions but medical examinations and tests may be the only way to determine their cause.


Source: American Cancer Society, Inc.