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 build-up of extra cells often forms a mass of tissue called a lump, growth, or tumor.