What Is Breast Cancer - Chapter 6 Breast Cancer Whos At Risk: Cancer

Content provided by the Faculty of the Harvard Medical School

What is breast cancer?

Breast cancer begins when cells in the breast tissue become abnormal and begin to multiply out of control, forming a tumor. Many tumors are benign and are caused by fibrocystic changes (fibrous thickening and cysts that cause lumpiness in the breast). Cysts are not cancerous and they don't spread outside the breast to other parts of your body.

But certain kinds of abnormal cells can begin to multiply out of control, becoming malignant. When a breast tumor is cancerous, it can spread beyond its initial site in the lobe or duct and invade adjacent breast tissue. Should it progress further, cancer can also reach either the lymph vessels (which normally carry fluids and immune system cells to and from the breast) or the bloodstream, which will allow it to spread to other, distant parts of the body.

Breast cancer also occurs in men, although it is rare. About 1,400 men are diagnosed annually - about one man for every 100 women who are diagnosed.

Early breast cancer produces no outward signs or symptoms, and even more advanced cancers may escape your notice. But as a tumor grows, a lump develops in the breast tissue. Other symptoms include breast discharge or dimpling. If breast cancer is found early, before it has spread, the five-year survival rate is 97%.

Last updated:	May 01, 2008