Kaposi sarcoma (KS) is a cancer that develops from the cells that line lymph or blood vessels. The abnormal cells of KS form purple, red, or brown blotches or tumors on the skin. These affected areas are called lesions. The skin lesions of KS may look bad, but in many cases, the lesions cause no symptoms. In other cases, the disease causes painful swelling, especially in the legs, groin area, or skin around the eyes. KS can cause serious problems (or even become life threatening) when the lesions are in the lungs, liver, or digestive tract. KS in the digestive tract, for example, can cause bleeding, while tumors in the lungs may cause difficulty breathing.

Types of Kaposi sarcoma

Some cancers such as lung cancer or breast cancer have several different types that indicate either different types of cells have become cancerous or different types of changes have occurred within a particular cell type. On the other hand, the different types of Kaposi sarcoma are defined by the different populations it develops in, but the changes within the KS cells are very similar.

Epidemic (AIDS-related) Kaposi sarcoma

The most common type of Kaposi sarcoma in the United States is epidemic or AIDS-related KS. This type of KS develops in people who are infected with HIV, the virus that causes AIDS. A person infected with HIV (that is, who is HIV-positive) does not necessarily have AIDS. The virus can be present in the body for a long time, typically many years, before causing major illness. The disease known as AIDS begins when the virus has seriously damaged the immune system, which results in certain types of infections and other medical complications, including KS. When HIV damages the immune system, people who also are infected with Kaposi sarcoma herpesvirus are more likely to develop KS. KS is considered to be an "AIDS defining" illness. This means that when KS occurs in someone infected with HIV, that person officially has AIDS (and is not just HIV positive).

Treatment of HIV infection with highly active antiretroviral therapy (HAART) has resulted in fewer cases of epidemic KS. It can often keep advanced KS from developing. HAART doesn't completely protect against KS -- it can still occur in people whose HIV is well controlled with HAART. Sometimes people on HAART get aggressive KS that requires treatment with chemotherapy, radiation, or some therapy. Once KS develops it is still important to continue HAART -- in areas of the world where HAART is not easy to obtain, KS in AIDS patients can advance quickly and cause death in just 6 months.

Classic (Mediterranean) Kaposi sarcoma

Classic Kaposi sarcoma occurs in elderly people of Mediterranean, Eastern European, and Middle Eastern heritage. Classic KS is more common in men than in women. Patients typically have one or more lesions on the legs, ankles, or the soles of the feet. Compared to other types of KS, the lesions in this type do not grow as quickly, and new lesions do not develop as often. The people who get classic KS come from areas where KS herpesvirus infection is more common than in the US or Northern Europe. The immune system of people with classic KS is not as weak as it is in those who have epidemic KS, but it may be weaker than normal. Getting older can naturally weaken the immune system a little. When this occurs, people who already have a KS herpesvirus infection are more likely to develop KS.

Endemic (African) Kaposi sarcoma

Endemic Kaposi sarcoma occurs in people living in Equatorial Africa and is sometimes called African KS. KS herpesvirus infection is much more common in Africa than in other parts of the world, increasing the risk of KS. There appear to be other factors in Africa that contribute to the development of KS since the disease affects a broader group of people that includes children and women.

Endemic KS tends to occur in younger people (usually under age 40). Rarely a more aggressive form of endemic KS is seen in children before puberty. This type usually affects the lymph nodes and other organs and can lead to death within a year.

Endemic KS used to be the most common type of KS in Africa. Then, as AIDS became more common in Africa, the epidemic type became the most common type seen in that area.

Iatrogenic (transplant-associated) Kaposi sarcoma

When Kaposi sarcoma develops in people whose immune systems have been suppressed after an organ transplant, it is called iatrogenic, or transplant-associated, KS. Most transplant patients need to take drugs to keep the immune system from rejecting (attacking and killing) the new organ. By weakening the body's immune system, these drugs increase the chance that someone infected with KSHV will develop KS. Stopping the immune suppressing drugs or lowering their dose often makes KS lesions disappear or get smaller.

Kaposi sarcoma in HIV negative men having sex with men

Recently, there have been reports of KS developing in men who have sex with men who are not infected with HIV. In this group, the cases of KS are often mild, similar to cases of classic KS.

Last Medical Review: 09/17/2009
Last Revised: 09/17/2009