A cell is the smallest building block of the body. Healthy cells grow and divide in an orderly way. This normal growing and dividing of cells is a life-long, continuous process. It is this process that causes us to grow, to replace worn out body tissues and to have bodily injuries heal. Sometimes, cells grow and divide when they are not needed.
Many unhealthy cells form too much tissue.
This mass of tissue is called a tumor. Any change in the breast, including a thickening or swelling in a local area that wasn't there before, may be a tumor. Many women will experience a benign tumor at one time or another. Benign tumors are not a threat to life, and can usually be removed. Unlike benign tumors, cancerous tumors continue to grow in an uncontrolled way and in time will spread beyond the breast.