Swelling in an arm or leg caused by a lymphatic system blockage. Lymph is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to be recirculated. Lymph nodes are an important part of your lymphatic system. Lymphedema can be caused by cancer treatments that remove or damage your lymph nodes. Any type of problem that blocks the drainage of lymph fluid can cause lymphedema. Treatment may include compression bandages, massage, compression stockings, sequential pneumatic pumping.