Cancer Cells

Cancer begins in cells, the building blocks that make up all tissues and organs of the body, including the breast.
Normal cells in the breast and other parts of the body grow and divide to form new cells as they are needed. When normal cells grow old or get damaged, they die, and new cells take their place.
Sometimes, this process goes wrong. New cells form when the body doesn't need them, and old or damaged cells don't die as they should. The buildup of extra cells often forms a mass of tissue called a lump, growth, or tumor.
Tumors in the breast can be benign (not cancer) or malignant (cancer):
Benign tumors:

• Are usually not harmful
• Rarely invade the tissues around them
• Don't spread to other parts of the body
• Can be removed and usually don't grow back

Malignant tumors:

• May be a threat to life
• Can invade nearby organs and tissues (such as the chest wall)
• Can spread to other parts of the body
• Often can be removed but sometimes grow back