Causes

The lymphatic system is a network of vessels that carry protein-rich lymph fluid throughout the body. It's part of your immune system. Lymph nodes act as filters and contain cells that fight infection and cancer.

The lymph fluid is pushed through the lymph vessels by muscle contractions as you move through the tasks of your day and small pumps in the wall of the lymph vessels. Lymphedema occurs when the lymph vessels are not able to adequately drain lymph fluid, usually from an arm or leg.

The most common causes of lymphedema include:

• Cancer. If cancer cells block lymph vessels, lymphedema may result. For instance, a tumor growing near a lymph node or lymph vessel could enlarge enough to block the flow of the lymph fluid.
• Radiation treatment for cancer. Radiation can cause scarring and inflammation of lymph nodes or lymph vessels.
• Surgery. In cancer surgery, lymph nodes are often removed to see if the disease has spread. However, this doesn't always result in lymphedema.
• Parasites. In developing countries in the tropics, the most common cause of lymphedema is infection with threadlike worms that clog the lymph nodes.

Less commonly, lymphedema results from inherited conditions in which the lymphatic system doesn't develop properly.