The breast is made up of glands called lobules that can make milk and thin tubes called ducts that carry the milk from the lobules to the nipple. Breast tissue also contains fat and connective tissue, lymph nodes, and blood vessels.
The most common type of breast cancer is ductal carcinoma, which begins in the cells of the ducts. Breast cancer can also begin in the cells of the lobules and in other tissues in the breast. Invasive breast cancer is breast cancer that has spread from where it began in the ducts or lobules to surrounding tissue.
U.S. Department of Health & Human Services
Breast Cancer Treatment (Adult) (PDQ®)–Patient Version
General Information About Breast Cancer
- Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast.
- A family history of breast cancer and other factors increase the risk of breast cancer.
- Breast cancer is sometimes caused by inherited gene mutations (changes).
- The use of certain medicines and other factors decrease the risk of breast cancer.
- Signs of breast cancer include a lump or change in the breast.
- Tests that examine the breasts are used to diagnose breast cancer.
- If cancer is found, tests are done to study the cancer cells.
- Certain factors affect prognosis (chance of recovery) and treatment options.
Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast.
The breast is made up of lobes and ducts. Each breast has 15 to 20 sections called lobes. Each lobe has many smaller sections called lobules. Lobules end in dozens of tiny bulbs that can make milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts.
Each breast also has blood vessels and lymph vessels. The lymph vessels carry an almost colorless, watery fluid called lymph. Lymph vessels carry lymph between lymph nodes. Lymph nodes are small, bean-shaped structures found throughout the body. They filter lymph and store white blood cells that help fight infection and disease. Groups of lymph nodes are found near the breast in the axilla (under the arm), above the collarbone, and in the chest.
The most common type of breast cancer is ductal carcinoma, which begins in the cells of the ducts. Cancer that begins in the lobes or lobules is called lobular carcinoma and is more often found in both breasts than are other types of breast cancer. Inflammatory breast cancer is an uncommon type of breast cancer in which the breast is warm, red, and swollen.
See the following PDQ summaries for more information about breast cancer:
A family history of breast cancer and other factors increase the risk of breast cancer.
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. Talk to your doctor if you think you may be at risk for breast cancer.
Risk factors for breast cancer include the following:
- A personal history of invasive breast cancer, ductal carcinoma in situ (DCIS), or lobular carcinoma in situ (LCIS).
- A personal history of benign (noncancer) breast disease.
- A family history of breast cancer in a first-degree relative (mother, daughter, or sister).
- Inherited changes in the BRCA1 or BRCA2 genes or in other genes that increase the risk of breast cancer.
- Breast tissue that is dense on a mammogram.
- Exposure of breast tissue to