Lymphedema is a collection of fluid called lymph in the tissues of the body. Normally, this fluid flows through the lymph system. If that system isn't working as it should, fluid can build up in the affected area and cause lymphedema. This happens most often in an arm or a leg.

Lymphedema may be caused by cancer treatment, like surgery or radiation. Or it may be caused by cancer itself, such as when tumors press against lymph nodes or affect the lymph system. Other causes include infections, inflammatory conditions, obesity, and injury to the lymph nodes. Sometimes the cause isn't known.

Lymphedema causes the blood vessels and lymph channels in an area of the body to increase in size and number. It also reduces oxygen delivery to the tissues, interferes with wound healing, and can lead to infection. Lymphedema is often a permanent condition and may not completely go away, even with treatment. The amount of swelling may fluctuate at different times.

Lymphedema is often managed with compression therapy, special massage, and self-care. Surgery is an option in some cases.