Overview

Kaposi's sarcoma is a type of cancer that forms in the lining of blood and lymph vessels. The tumors (lesions) of Kaposi's sarcoma typically appear as painless purplish spots on the legs, feet or face. Lesions can also appear in the genital area, mouth or lymph nodes. In severe Kaposi's sarcoma, lesions may develop in the digestive tract and lungs.

The underlying cause of Kaposi's sarcoma is infection with a virus called human herpesvirus 8 (HHV-8). In healthy people, HHV-8 infection usually causes no symptoms because the immune system keeps it under control. In people with weakened immune systems, however, HHV-8 has the potential to trigger Kaposi's sarcoma.

People infected with human immunodeficiency virus (HIV) — the virus that causes AIDS — have the highest risk of Kaposi's sarcoma. The immune system damage caused by HIV allows cells harboring HHV-8 to multiply. Through unknown mechanisms, the characteristic lesions form.

Recipients of organ transplants who take immune system-suppressing drugs to prevent transplant rejection also are at risk of Kaposi's sarcoma. In this population, though, the disease tends to be milder and easier to control than it is in people with AIDS.

Another type of Kaposi's sarcoma occurs in older men of Eastern European, Mediterranean and Middle Eastern descent. Known as classic Kaposi's sarcoma, this cancer progresses slowly and typically causes few serious problems.

A fourth type of Kaposi's sarcoma that affects people of all ages occurs in equatorial Africa.