Kaposi’s sarcoma, a type of soft tissue tumor, originates in cells that normally develop into blood or lymph vessels, and usually appears first in the skin. The disease was uncommon in the United States before it began appearing in people with AIDS in the early 1980s. Before AIDS, the forms of Kaposi’s sarcoma that had been observed were usually milder, occurring primarily in middle-aged and elderly men of Mediterranean and European descent. Several forms of Kaposi’s sarcoma also occur in children and adults in sub-Saharan Africa. Kaposi’s sarcoma is more common in people who are receiving drugs to prevent rejection of transplanted organs, such as the kidney.
Kaposi’s sarcoma is often classified into one of four groups:
- Classic — A generally slow-growing form that remains on the skin and is most common in older men of Jewish or Mediterranean descent. Patients may have an increased risk of other cancers.
- African — Occurs mostly in adults and children from central and east Africa. It can be more aggressive than classic Kaposi’s sarcoma.
- Transplant, or Immunosuppression Associated — Occurs in people who have had an organ transplant and are taking medications to suppress their immune systems.
- AIDS associated — An epidemic form that occurs in people with AIDS and often spreads faster and more widely in the body than the other forms.
Kaposi’s sarcoma and pneumocystis pneumonia were the first diseases associated with AIDS. For many years, Kaposi’s sarcoma was the most common cancer in AIDS patients. Its incidence has decreased in the United States in the last decade, but is still a very serious problem in the developing world. Kaposi’s sarcoma is one of the most common cancers diagnosed in sub-Saharan Africa.
Light-skinned people with Kaposi’s sarcoma develop flat or raised spots or bumps that are pink, red, or purple in color. They appear brown to black in dark-skinned people. Lesions can develop anywhere on the body, but often appear first on the tip of the nose, the legs, or the soles of the feet. The lesions are caused by abnormal blood vessels that grow in a distorted and disorganized fashion, and by blood cells that leak out of these blood vessels.
About a third of patients with AIDS-associated Kaposi’s sarcoma develop lesions inside the mouth. AIDS-associated Kaposi’s sarcoma is often much more aggressive than classic Kaposi’s sarcoma.
Kaposi’s sarcoma lesions are generally not painful, but they sometimes do cause pain that can be debilitating. Lesions on the feet, for example, may make walking difficult. These lesions are treatable and usually not life threatening unless the internal organs are affected.
Other symptoms may include:
- Abdominal pain, blockage of the intestine, or gastrointestinal bleeding, which may occur if lesions develop in the gastrointestinal tract.
- Shortness of breath, cough, wheezing, coughing up blood, and respiratory failure when lesions involve the lungs.
- Lymph node enlargement if Kaposi’s sarcoma arises in the lymph nodes. Enlarged lymph nodes are also a symptom of other illnesses associated with AIDS.
- Lymphedema (excess of fluid and swelling), especially in the legs and feet, the genital area, and around the eyes.
People with all types of Kaposi’s sarcoma tumors are infected with a virus called human herpesvirus 8 (HHV-8), also known as Kaposi’s sarcoma-associated herpesvirus (KSHV). Infection with this virus is necessary for Kaposi’s sarcoma to develop, but not everyone who is infected with the virus develops Kaposi’s sarcoma.
Exactly how HHV-8 is passed from one person to another is not completely understood. Men who have sex with men are more likely to develop Kaposi’s sarcoma than other people with HIV infection. People who have been infected with HIV through intravenous drug use or heterosexual intercourse also have an increased risk of developing Kaposi’s sarcoma. The virus may also pass from person to person through other routes.
Immunodeficiency is an important risk factor for Kaposi’s sarcoma. Even before the AIDS epidemic, doctors noted that Kaposi’s sarcoma tended to occur more often in patients with weakened immune systems, for instance, in people who take immunosuppressive drugs to prevent the rejection of a transplanted organ. Up to 5 percent of kidney transplant recipients have been reported to develop Kaposi’s sarcoma.
Most forms of Kaposi’s sarcoma are more common in men than in women, but the reason for this difference is not known.