Breast cancer develops when abnormal breast cells begin to grow
out of control. When a group of these cells band together, they form
a mass called a tumor. Benign tumors do not spread and are usually
not harmful. Malignant tumors, however, spread from their sources
and can grow into life-threatening cancers. When a malignant cell
leaves the breast and invade other parts of the body — a process
called metastasis — the chance of successfully treating the
disease is greatly diminished. |