Whether you have a mastectomy or breast-conserving surgery (lumpectomy) for breast cancer, your doctors need to know whether the cancer has spread to the lymph nodes. Lymph node involvement increases the likelihood that cancer cells have spread through the bloodstream to other parts of the body. Women with some forms of very early breast cancer, such as ductal or lobular carcinoma in situ, do not need lymph node testing.

There are two ways for your doctor to check the lymph nodes under your arm. They are:

• Surgery with a procedure called axillary lymph node dissection. During this surgery, 10 to 20 lymph nodes in the armpit are removed and checked for cancer cells. Removal of the axillary lymph nodes can cause significant, long-term swelling (lymphedema) in some women. Doctors have tried to develop new ways of detecting the spread of cancer to lymph nodes that do not involve removing as many lymph nodes.
• Sentinel lymph node biopsy. This is a procedure in which tissue is removed from the lymph node closest to the cancer—the sentinel node (SN) or group of nodes—to help determine whether breast cancer has spread to this area. Sentinel lymph node biopsy does not cause as many problems with lymphedema. If the sentinel node does not contain cancer cells, the person may avoid more lymph node surgery and the side effects that may result from it. However, if the sentinel node contains cancer cells, the surgeon will then usually remove the other lymph nodes in the armpit.

Doctors once believed that removing as many lymph nodes as possible would improve chances for cure. However, lymph node surgery itself does not improve your chances for a cure. Treatment with hormone therapy or chemotherapy offers the best chance of destroying cancer cells that have spread beyond the breast.