What is cancer?

Cancer starts when cells in the body change (mutate) 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 doesn't need them any longer.

Cancer is made up of changed (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 spread to other parts of the body, too. This is called metastasis.

What is Kaposi sarcoma?

In Kaposi sarcoma (KS), cancer starts in the cells that line lymph or blood vessels. It is a type of soft tissue sarcoma. KS gets its name from Dr. Moritz Kaposi, who first described it in 1872.

KS forms as raised purple, brown, red, blue, or black patches or nodules on 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're not usually life-threatening. In most cases, the lesions cause no symptoms. Sometimes, though, the lesions can cause pain or swelling of the skin. And when KS involves organs like the liver, lungs, digestive system, or lymph nodes, other symptoms can develop. For instance, 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. This virus can cause certain types of cells to grow out of control, which might lead to cancer. Still, most people infected with HHV-8 don't develop KS. People infected with HHV-8 who also have weak immune systems—due to things like HIV, malnutrition, or other ongoing (chronic) infections—are more likely to have KS.

What are the types of Kaposi sarcoma?

There are four main types of Kaposi sarcoma. The KS cancer cells look much the same in all of them.

AIDS-related or epidemic KS

This is the most common type of KS in the U.S. It's found in people who are infected with HIV, the virus that causes AIDS.

If not treated, HIV infection can weaken the immune system over time. This leaves 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, like lymph nodes, the lungs, spleen, liver, and other organs.

Classic KS

This type of KS is mostly seen in older men who are of Jewish or Mediterranean, Eastern European, or Middle Eastern descent.

The lesions tend to be on the legs or feet. They often grow 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, but this is more common in other forms of KS.

Endemic or African KS

This type occurs in adults and children in certain areas of Africa along the equator. It's a lot like the classic form of KS, but it tends to develop at a younger age. Children often have a more aggressive form of the disease.

African KS often affects skin, lymph nodes, and other organs.

Iatrogenic, acquired, or transplant-associated KS

This kind of KS is found in people who are taking medicines to make their immune system weaker. This includes people who have had an organ transplant and need to keep their immune system from rejecting the new organ. Lowering the doses of immune-suppressing medicines can often help keep the KS under control. Usually, this type of KS affects only the skin. But it can spread to other organs or to mucous membranes.

Talk with your healthcare provider

If you have questions about Kaposi sarcoma, talk with your healthcare provider. Your provider can help you understand more about this cancer.