The breast is made up of lobes and ducts. Each breast has 15 to 20 sections called
lobes, which have many smaller sections called lobules. Lobules end in dozens of tiny bulbs that
can produce milk. The lobes, lobules, and bulbs are linked by thin tubes called
Each breast also contains blood vessels and lymph vessels. The lymph vessels carry an almost colorless fluid called lymph. Lymph vessels lead to organs called lymph nodes. Lymph nodes are small bean-shaped structures that are found throughout the body. They filter substances in lymph and help fight infection and disease. Clusters of lymph nodes are found near the breast in the axilla (under the arm), above the collarbone, and in the chest.
Women in the United States get breast cancer more than any other type of cancer except for skin cancer. Breast cancer is second only to lung cancer as a cause of cancer death in women. Breast cancer occurs in men also, but the number of cases is small.
Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. Risk factors for breast cancer include: