Each lobe has many smaller lobules , which end in dozens of tiny milk-producing bulbs. The lobes, lobules, and bulbs are all linked by thin tubes called ducts . These ducts lead to the nipple in the center of a dark area of skin, called the areola . Fat fills the spaces between the other parts of the breast. Muscles cover the ribs and lie under the breast, but they are not part of the breast.
Cancer is a group of diseases.
More than 100 different types of cancer are known-and there are several types of breast cancer. Healthy cells that make up the body's tissues grow, divide, and replace themselves in an orderly way. This process keeps the body in good repair. Sometimes, however, some cells lose the ability to control their growth. They grow too rapidly and without any order.