Kaposi Sarcoma

What Is Kaposi Sarcoma?

Kaposi sarcoma (KS) is a cancer that develops from the cells that line lymph or blood vessels. KS is caused by the Kaposi sarcoma herpesvirus (KSHV), which is also called human herpesvirus 8. Although people do not develop KS without first getting infected with KSHV, most people who are infected with KSHV never develop KS. Someone who is infected with KSHV is more likely to develop KS if their immune system doesn’t work properly. The most common immune system problem that contributes to KS is infection with the human immunodeficiency virus (HIV).

The abnormal cells of KS form purple, red, or brown blotches or tumors on the skin. These affected areas are called lesions. Although the skin lesions of KS may look bad, 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 KS 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 (KS) 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. When HIV damages the immune system, people who also are infected with Kaposi sarcoma herpesvirus are more likely to develop KS.

Treatment of HIV infection with highly active antiretroviral therapy (HAART) has decreased the incidence of epidemic KS and can often keep advanced KS from developing. Not everyone whose HIV is well controlled is protected from KS, and sometimes aggressive KS develops that requires the use of chemotherapy or other treatments. 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 (KS) 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. In comparison with 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 weakened as those who have epidemic KS. But, getting older may naturally weaken their immunity a little, which makes people more likely to develop KS if they already have a KS herpesvirus infection.

Endemic (African) Kaposi sarcoma

Endemic Kaposi sarcoma (KS) 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 chance of KS developing. 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.

Iatrogenic (transplant associated) Kaposi sarcoma

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

Do We Know What Causes Kaposi Sarcoma?

Kaposi sarcoma is caused by a virus called the Kaposi sarcoma herpesvirus (KSHV), also known as human herpesvirus 8 (HHV8). KSHV belongs to the herpesvirus family and is similar to Epstein-Barr virus, the virus that causes infectious mononucleosis ("mono") and contributes to several types of cancer. KSHV has to be present in the tumor cells of Kaposi’s sarcoma for it to develop. Endothelial cells, which are cells that line blood and lymphatic vessels, are infected with KSHV in KS. Although scientists do not yet completely understand how KSHV causes KS, they do know that the virus brings genetic material into the cells that causes them to divide too much and invade surrounding tissues.

KSHV infection is much more common than KS, and most people infected with this virus do not get KS. The percentage of people infected with KSHV is different in different places around the world. In the United States, studies have found infection rates ranging from 5% to 25% in different parts of the country, and KSHV is more commonly found in gay men.

In some areas of Africa, more than 90 % of the population shows signs of KSHV infection. In these areas the virus seems to spread from mother to child. KSHV is more commonly detected in saliva than in other body fluids. Many people infected with KSHV will never show any symptoms. A very small number of those infected will get a mild type of KS. In people whose immune systems are weakened (by AIDS, for example) infection with KSHV is much more likely to lead to KS.

Can Kaposi Sarcoma Be Found Early?

Most cancers start in one place and then spread to other parts of the body. When these cancers are found early, they are more likely to be curable. KS is very different. KS tends to form in several areas at the same time. Even when only 1 skin lesion is visible, many patients already have other areas of KS that are just too small to be seen.

People infected with HIV should be regularly examined by health care providers familiar with diagnosing KS and other manifestations of AIDS. Patients who are aware of the signs and symptoms of KS and other AIDS-related problems should tell their doctors so they can receive treatment promptly, if they need it.

How Is Kaposi Sarcoma Treated?

This information represents the views of the doctors and nurses serving on the American Cancer Society's Cancer Information Database Editorial Board. These views are based on their interpretation of studies published in medical journals, as well as their own professional experience.

The treatment information in this document is not official policy of the Society and is not intended as medical advice to replace the expertise and judgment of your cancer care team. It is intended to help you and your family make informed decisions, together with your doctor.

Your doctor may have reasons for suggesting a treatment plan different from these general treatment options. Don't hesitate to ask him or her questions about your treatment options.

Treatment for KS is more effective than it was a couple of decades ago. Doctors now better understand what causes KS. Many clinical trials have been done to compare different approaches to treatment. Doctors have much more experience with KS than they did when this disease was quite rare. Choices about the best treatment options for each patient are based on the function of the immune system as well as the number, location and size of the KS lesions. The patient's general condition is also a major factor. The presence and severity of other serious medical conditions can make some treatments a poor choice. Some of the treatments used for KS are surgery, chemotherapy, radiation therapy, and biological therapy. In some cases, 2 or more of these treatments are used together.

Treating immune deficiency and related infections

The most important treatment for KS is to treat any immune deficiency that exists as well as any related infections. In people with AIDS, this means using highly active antiretroviral therapy (HAART) (specific anti-HIV drugs). For many AIDS patients with KS, HAART may be the only treatment needed. for the KS. In organ-transplant patients who are immune suppressed because they are taking medicines, decreasing or changing the drugs may be helpful. New KS lesions are more likely to develop when a patient's blood test results for KS herpesvirus (KSHV) are positive. The risk of developing new lesions is lower when antiviral medicines such as ganciclovir or foscarnet are used. In contrast, existing lesions are relatively resistant to treatment with antiviral agents. KS lesions tend to get worse when patients develop infections with bacteria. Therefore, it is very important to take measures to prevent bacterial infections and to treat them promptly and effectively if they do occur.