The lymphatic system consists of lymph vessels and lymph nodes throughout the body. These vessels collect lymphatic fluid which is composed of protein, water, fats, and waste products from your cells. The collection of lymphatic fluid is then transported to the lymph nodes where waste products and foreign materials are filtered out, somewhat like a water filtration system. This filtered fluid is returned to the blood by the lymph vessels. The swelling in lymphedema is caused by abnormal accumulation of the lymph fluid in the tissue and impedes the system to not perform its function. Causes the lymphatic system to develop insufficient removal, infection, and radiation of the lymph nodes (called secondary lymphedema), or developmental causes (called secondary lymphedema). Therapy is important at all stages for reducing the swelling with specialized massage techniques and exercise.