Understanding the BreastsThe breasts sit on the chest muscles that cover the ribs. 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 ducts. Milk flows from the lobules through these ducts to the nipple. The nipple is in the center of a dark area of skin called the areola. Fat fills the spaces between the lobules and ducts.
Each breast also contains blood vessels and lymph vessels. The lymph vessels carry an almost colorless fluid called lymph. These vessels lead to organs called lymph nodes. In breast cancer, the cancer cells can spread outside the breast into the lymph nodes under the arm. In many cases, if the cancer has reached the lymph nodes, cancer cells may have also spread to other parts of the body via the lymphatic system or through the bloodstream.
(Click Breast Anatomy for more information.)
Types of Breast CancerBreast cancer can be invasive (moves into the surrounding tissue) or non-invasive (stays in the ducts or lobes). Invasive breast cancers make up 70 to 80 percent of all cases. The most common type of invasive breast cancer is infiltrating ductal carcinoma (also called invasive ductal carcinoma). This type is found in approximately 60 percent of cases.
Other types of breast cancer include:
- Infiltrating lobular carcinoma (also called invasive lobular carcinoma)
- Intraductal carcinoma, also known as ductal carcinoma in situ (DCIS)
- Lobular carcinoma in situ (LCIS)
- Paget's disease of the nipple
- Inflammatory breast cancer.