Lymphedema is an accumulation of fluid and swelling of tissues due to insufficient drainage of fluid by the lymphatic system. In the United States, lymphedema occurs most often after breast cancer treatment and it has been estimated that 13% of American women will develop breast cancer during their lifetimes. Women whose breast cancer has spread to nearby lymph nodes often require surgical removal or irradiation of the affected nodes; however, these treatments damage the lymphatic system and may cause lymphedema, a serious complication that affects 6% to 40% of breast cancer survivors. In addition to increasing the likelihood of infection, lymphedema impairs quality of life cosmetically and physically with symptoms such as arm tightness, heaviness, weakness, and loss of sensation. The risk of lymphedema varies depending on the number of lymph nodes removed and the location and amount of radiation received in addition to surgery.