A woman with breast cancer has a growth of abnormal cells in the breast that multiply out of control. These cells can form tumors and spread to other parts of the body.

Breast cancer is the most common form of cancer in women. About two-thirds of women with breast cancer develop a breast lump that is detected on physical examination.

Breast cancer can cause a variety of other changes in the skin and nipple of the affected breast.

In one third of cases, detecting breast cancer requires a mammogram.