When the impairment becomes so great that the lymphatic fluid exceeds the lymphatic transport capacity, an abnormal amount of fluid collects in the tissues of the affected area. Left untreated, this stagnant, protein-rich fluid not only causes tissue channels to increase in size and number, but also reduces oxygen availability in the transport system, interferes with wound healing, and provides a culture medium for bacteria that can result in lymphangitis infection and possibly death.
In the USA most lymphedema arises following cancer treatments, particularly melanomas, and cancers of the breast, reproductive organs and prostate. Surgical removal of the cancer demands removal of the nearby lymph nodes; radiation treatment for cancer can also damage lymph vessels, and affects about 20% of cancer treatments that spare the breasts.