Cancer begins in the cells which are the basic building blocks that make up tissue. The tissue is found in the breast and other parts of the body.  Sometimes, the process of cell growth goes wrong and new cells form when the body doesn’t need them and old or damaged cells do not die as they should.  When this occurs, a build up of cells often forms a mass of tissue called a lump, growth, or tumor.

Breast cancer occurs when malignant tumors develop in the breast.  These cells can spread by breaking away from the original tumor and entering blood vessels or lymph vessels, which branch into tissues throughout the body. When cancer cells travel to other parts of the body and begin damaging other tissues and organs, the process is called metastasis.