Cancer is the name for a group of more than 100 diseases in which cells begin to grow out of control. Cancer can develop anywhere in the body. It starts when cells grow out of control and crowd out normal cells.
The development of malignant cells in the breast. The malignant cells originate in the lining of the milk glands or ducts of the breast (ductal epithelium), defining this malignancy as a cancer. Cancer cells are characterized by uncontrolled division leading to abnormal growth and the ability of these cells to invade normal tissue locally or to spread throughout the body, in a process called metastasis.