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 AIDS patients 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.
