It uses the milk pipes, or ducts, to drain that milk out to the nipple. Like all parts of your body, the cells in your breasts usually grow and then rest, grow and rest. These periods of growth and rest are controlled by the genes in the cell's nucleus, which is like the control room of each cell. When your genes are in good working order, they keep cell growth under control. But when your genes develop an abnormality, they sometimes lose their ability to control cell growth and rest.
Breast cancer is an uncontrolled growth of breast cells.
Cancer has the potential to break through normal breast tissue barriers and spread to other parts of the body. Or maybe your cells just made a mistake one day when they were making new genes to pass on to their baby cells. Feeling guilty, or telling yourself that breast cancer happened because of something you or anyone else did, is counterproductive. As soon as you're diagnosed with breast cancer, you desperately try to figure out how it could have happened. You analyze your life a thousand times over, rack your brains searching for THE reason, beat your head against the wall, experience endless guilt.