Cancer begins when normal cells change and grow uncontrollably, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can spread to other parts of the body. A benign tumor means the tumor will not spread.
Kaposi sarcoma is a type of soft-tissue sarcoma. Soft-tissue sarcomas are a group of cancers that begin in the tissues that support and connect the body. Kaposi sarcoma generally develops in tissue located below the skin's surface or in the mucous membranes of the mouth, nose, or anus. Areas of abnormal tissue change, known as Kaposi sarcoma lesions, usually appear on the skin as raised blotches or nodules. These lesions may be purple, red, or brown. When viewed under a microscope, Kaposi sarcoma cells resemble blood vessels.
There are several types of Kaposi sarcoma:
Classic Kaposi sarcoma. Classic Kaposi sarcoma traditionally occurs in older men of Jewish or Mediterranean descent. Lesions most often appear on the lower body, particularly on the legs, ankles, or soles of the feet. Classic Kaposi sarcoma is more common in men than women, and lesions may develop over a period of 10 to 15 years.
Endemic Kaposi sarcoma. Endemic or African Kaposi sarcoma usually develops in people living in equatorial Africa. Most often, Endemic Kaposi sarcoma is the same as classic Kaposi sarcoma, but people generally develop the disease at a younger age. A particularly aggressive form of Endemic Kaposi sarcoma can develop in children who have not yet reached puberty. It usually involves the lymph nodes and other organs. Endemic Kaposi sarcoma usually causes skin lesions without any other symptoms, and these lesions do not spread to other parts of the body.
Acquired Kaposi sarcoma. Acquired, immunosuppressive treatment-related, or transplant-related Kaposi sarcoma develops in people who have received an organ transplant and are taking drugs to suppress their immune system to prevent their body from rejecting the transplanted organ. Because this treatment lowers the function of the immune system, secondary diseases or infections can occur. Kaposi sarcoma is 150 to 200 times more likely to develop in people who have received an organ transplant than in the general population. Most of the time, acquired Kaposi sarcoma only affects the skin, but the disease can spread to the mucous membranes or other organs.
Epidemic Kaposi sarcoma. Kaposi sarcoma in people with HIV/AIDS is often called epidemic Kaposi sarcoma. Acquired immune deficiency syndrome (AIDS) is a disease of the immune system caused by infection with the human immunodeficiency virus (HIV). It is the most common type of Kaposi sarcoma. Today, Kaposi sarcoma is found most often in homosexual men with HIV/AIDS. Epidemic Kaposi sarcoma causes lesions to form in many different areas on the body. It may affect the lymph nodes and organs, such as the liver, spleen, lungs, and the digestive tract. Learn more about HIV/AIDS-related cancer.