Save 25% on Ear Drops and premeasured dose pump Nasal Sprays with grapefruit seed extract! Made without gluten. Vegan.ave 25% on Ear Drops and premeasured dose pump Nasal Sprays with grapefruit seed extract! Made without gluten. Vegan.
By Mayo Clinic Staff. Cancer is caused by changes (mutations) to the DNA within cells. The DNA inside a cell is packaged into a large number of individual genes, each of which contains a set of instructions telling the cell what functions to perform, as well as how to grow and divide.
It's not clear what causes breast cancer. Doctors know that breast cancer occurs when some breast cells begin growing abnormally. These cells divide more rapidly than healthy cells do and continue to accumulate, forming a lump or mass. The cells may spread (metastasize) through your breast to your lymph nodes or to other parts of your body.