Lymphedema (from the Latin word lympha, meaning: “clear water” and edema, Greek for “swelling”) is swelling, typically of an arm or leg, because lymph fluid is building up. A breast or another part of the body may be affected as well. Lymph is a clear fluid that circulates through the entire body and plays a role in our immune system, among other things. Lymphedema results when the flow of lymph is affected by damage to the lymph vessels or lymph nodes and the fluid starts to build up in the tissue.