Cancer is when cells in the body change and grow out of control. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them, and die when your body does not need them any longer.
Cancer is made up of abnormal cells that grow even though your body doesn't need them. In most cancers, the abnormal cells grow to form a lump or mass called a tumor. If cancer cells are in the body long enough, they can grow into (invade) nearby areas. They can even spread to other parts of the body (metastasis).
In Kaposi sarcoma (KS), cancer develops from the cells that line lymph or blood vessels. KS gets its name from Dr. Moritz Kaposi, who first described it.
KS forms as purple, brown, or red patches just under the skin, in mucous membranes (like the inside of the nose, mouth, or anus), or in internal organs. These patches are called lesions. KS lesions can be deforming, but they are not usually life-threatening. In most cases, the lesions cause no symptoms. Sometimes, though, the lesions can cause pain or swelling of the skin. When KS involves organs such as the liver, lungs, digestive system, or lymph nodes, other symptoms can develop. For example, KS tumors in the lungs can cause breathing problems.
KS is linked to infection with human herpes virus 8 (HHV-8), also known as the Kaposi sarcoma-associated herpes virus (KSHV). This virus can cause certain types of cells to grow out of control, which might lead to cancer. However, most people infected with HHV-8 don't develop KS. KS appears most often in people infected with HHV-8 who also have a weak immune system.
There are several types of Kaposi sarcoma:
AIDS-related (epidemic) KS. The most common type of KS in the U.S. occurs in people who are infected with HIV, the virus that causes AIDS. If not treated, HIV infection can weaken the immune system over time, which can leave the body less able to fight off infections from other viruses. In people who are already infected with HHV-8, this makes them more likely to develop KS. This type of KS often causes lesions to form in many parts of the body.
Classic KS. This type usually appears in older men who are of Jewish or Mediterranean descent. It tends to appear as lesions on the legs or feet and often grows slowly, sometimes over 10 to 15 years. As the disease gets worse, the lower legs may swell due to poor circulation and pooling of blood and other fluids. KS can spread to other organs over time as well, but usually less often than in other forms of KS.
Endemic (African) KS. This type occurs in men, women, and children in certain areas of Africa. It's similar to the classic form of KS, although it typically develops at a younger age. Children usually have a more aggressive form of the disease.
Iatrogenic (transplant-associated) KS. This kind of KS may show up in people who are taking medicines to make their immune system weaker. This includes people who have had an organ transplant and need to stop their immune system from rejecting the new organ. Lowering the doses of immune-suppressing medicines can often help keep the KS under control.
If you have questions about Kaposi sarcoma, talk with your healthcare provider. Your provider can help you understand more about this cancer.