Kaposi's sarcoma is a cancer that causes patches of abnormal tissue to grow under the skin, in the lining of the mouth, nose, and throat or in other organs. The patches are usually red or purple and are made of cancer cells and blood cells. The red and purples patches often cause no symptoms, though they may be painful. If the cancer spreads to the digestive tract or lungs, bleeding can result. Lung tumors can make breathing hard.

Before the AIDS epidemic, KS usually developed slowly. In AIDS patients, though, the disease moves quickly. Treatment depends on where the lesions are and how bad they are. Treatment for the AIDS virus itself can shrink the lesions. However, treating KS does not improve survival from AIDS itself.

A sarcoma is a cancer that develops in connective tissues such as cartilage, bone, fat, muscle, blood vessels, or fibrous tissues (related to tendons or ligaments). Kaposi sarcoma (KS) was named for Dr. Moritz Kaposi who first described it in 1872.

For decades KS was considered a rare disease that mostly affected elderly men of Mediterranean or Jewish heritage, organ transplant patients, or young adult African men. This type is called classic Kaposi sarcoma. In the last 20 years, however, most KS cases have developed in association with human immunodeficiency virus (HIV) infection and the acquired immunodeficiency syndrome (AIDS), especially among homosexual men. This is called AIDS-related Kaposi sarcoma. With new treatments for AIDS and greater awareness of how HIV infection is acquired, the number of KS cases due to HIV infection has decreased about 85% to 90%. For example, in the Seattle,Washington area, the number of people diagnosed with Kaposi sarcoma has gone from 366 in the early 90's to 40 in more recent years.

This disease typically causes tumors to develop in the tissues below the skin surface, or in the mucous membranes of the mouth, nose, or anus. These lesions (abnormal tissue areas) appear as raised blotches or lumps that may be purple, brown, or red. Sometimes the disease causes painful swelling, especially in the legs, groin area, or skin around the eyes.

Although the skin lesions of KS may be disfiguring, they usually are not life threatening or disabling. In most cases, the lesions cause no symptoms. In some, the lesions may be painful, especially if they cause swelling of nearby unaffected skin. KS does become life threatening when it is in the lungs, liver, or gastrointestinal tract. This can cause major symptoms. KS in the gastrointestinal tract, for example, can produce bleeding, while tumors in the lungs may cause difficulty breathing.

There are several types of KS. They all differ in patterns of symptoms and organs likely to be affected, how aggressively the cancer grows and spreads, risk factors, and other personal characteristics of patients. The treatment used and the patient's likelihood of survival depend on the type of KS, as well as other factors discussed later in this document.

Classic Kaposi Sarcoma

Classic Kaposi sarcoma was first described in Jewish men of Eastern European origin or among men of Mediterranean heritage (primarily Italian) between the ages of 50 and 70. Classic KS is quite rare, even in these ethnic and age groups. In the past, 10 to 15 men were affected for every woman with classic KS. But even in the pre-AIDS era women were starting to become affected more often and now the ratio is more like 4 men for every woman. Patients typically have one or more lesions on the hands and arms and legs, ankles, or the soles of the feet. The lesions slowly get bigger and new lesions may develop over the course of 10 to 15 years. Pressure from the lesions can block lymph vessels causing swelling that may be painful. Lesions can also develop in the gastrointestinal tract, lymph nodes, and elsewhere in the body, although they rarely cause symptoms.

African (Endemic) Kaposi Sarcoma

African (or endemic) Kaposi sarcoma is a form of the disease that develops in people living in Equatorial Africa. This disease is fairly common. It accounts for 9% of all the cancers seen among Ugandan men, for example. In many cases, this disease is identical to classic KS, although it usually develops at a much younger age. It affects many more men than women. Typically, African (endemic) KS causes skin lesions that do not produce symptoms and do not spread to other parts of the body. However, more aggressive cases do occur, and some skin tumors may penetrate the underlying bone. Another form of the disease strikes children before puberty, affecting 3 times as many boys as girls, and usually involves the lymph nodes and other organs. In most cases, it leads to death within 3 years.

Transplant-Related (Acquired) Kaposi Sarcoma

Transplant-related (or acquired) Kaposi sarcoma develops in people whose immune systems have been suppressed after an organ transplant. Usually a transplant patient must take drugs to prevent the immune system from rejecting the newly transplanted organ. Because these drugs weaken the body's defenses, other diseases or infections can take hold. Kaposi sarcoma is 150 to 200 times more likely to develop in transplant patients than in the general population. Often, transplant-related KS affects only the skin. In some cases, though, the disease can spread to the mucous membranes or other organs.

AIDS-Related (Epidemic) Kaposi Sarcoma

AIDS-related (or epidemic) Kaposi sarcoma develops in people who are infected with the human immunodeficiency virus (HIV). Early in the AIDS epidemic, doctors began to see an unusual and sudden appearance of this form of KS. This led them to realize a new disease had emerged. Acquired immune deficiency syndrome (AIDS) results from infection by HIV. This virus destroys certain cells of the immune system, making the body unable to fight infections caused by certain other viruses, bacteria, and parasites. Certain cancers are also more likely to develop in people whose immune systems have been damaged.

A person infected with HIV (that is, being HIV-positive) does not necessarily have AIDS. The virus can be present in the body for a long time, typically many years, before causing any 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.

Certain diseases occur so often in people with AIDS that they are considered AIDS-defining conditions - that is, their presence in a person infected with HIV is a clear sign that full-blown AIDS has developed. The Centers for Disease Control and Prevention has identified certain cancers as AIDS-defining diseases: Kaposi sarcoma, lymphoma (especially non-Hodgkin lymphoma and primary central nervous system lymphoma), anal cancer, and cancer of the cervix that has spread to neighboring tissue (called invasive cervical cancer). Many other kinds of cancer may be more likely to develop in people who are HIV-positive. Of course, people without HIV or AIDS can also have these types of cancer.

In most cases, epidemic KS causes widespread lesions that erupt at many places on the body soon after AIDS develops. Lesions of epidemic KS may develop on the skin and in the mouth and may affect the lymph nodes and other organs, usually the gastrointestinal tract, lung, liver, and spleen. In contrast, classic KS usually affects only one or a few areas of skin, most often the lower legs. When they are diagnosed, however, some people with epidemic KS have no symptoms, especially if their lesions only develop on the skin. However, many - even those with no skin lesions - have swollen lymph nodes, unexplained fever, or weight loss. Eventually, in almost all patients, epidemic KS spreads throughout the body. Extensive lung involvement by KS can be fatal. This happens rarely, however, because modern treatment of the HIV infection usually prevents advanced Kaposi sarcoma from developing.