Kaposi’s sarcoma is a type of cancer that forms in the lining of blood and lymph vessels. The tumors (lesions) of Kaposi’s sarcoma typically appear as painless purplish spots on the legs, feet or face. Lesions can also appear in the genital area, mouth or lymph nodes. In severe Kaposi’s sarcoma, lesions may develop in the digestive tract and lungs.
The underlying cause of Kaposi’s sarcoma is infection with a virus called human herpesvirus 8 (HHV-8). In healthy people, HHV-8 infection usually causes no symptoms because the immune system keeps it under control. In people with weakened immune systems, however, HHV-8 has the potential to trigger Kaposi’s sarcoma.
People infected with human immunodeficiency virus (HIV) — the virus that causes AIDS — have the highest risk of Kaposi’s sarcoma. The immune system damage caused by HIV allows cells harboring HHV-8 to multiply. Through unknown mechanisms, the characteristic lesions form.
Recipients of organ transplants who take immune system-suppressing drugs to prevent transplant rejection also are at risk of Kaposi’s sarcoma. In this population, though, the disease tends to be milder and easier to control than it is in people with AIDS.
Another type of Kaposi’s sarcoma occurs in older men of Eastern European, Mediterranean and Middle Eastern descent. Known as classic Kaposi’s sarcoma, this cancer progresses slowly and typically causes few serious problems.
A fourth type of Kaposi’s sarcoma that affects people of all ages occurs in equatorial Africa.
Signs and symptoms of Kaposi’s sarcoma
The signs and symptoms are different, depending on whether you have external KS on the skin or KS inside the body. Lesions on the skin are more common than internal lesions inside the body.
Kaposi’s sarcoma of the skin
Lesions on the skin usually start out very small and flat. They do not cause any pain or itching and seem harmless. They look like a bruise but do not lose their colour when pressed, as a bruise does.
As they grow, they might start to stick up above the surrounding skin and grow into each other. The lesions might be in different colours such as brown, blue, red or deep purple.
Occasionally, the lesions form lumps (nodules) that can become ulcerated and that can bleed. The lumps are associated with painful swelling (oedema).
KS in the skin might grow very slowly and show no changes for a few months. But some grow more quickly, with new areas appearing weekly.
Internal Kaposi’s sarcoma
Internal KS lesions can grow in the lymph nodes and body organs, such as the lungs, liver, spleen and digestive system. The symptoms you have depend on which organs are affected.
The most common type of KS is related to AIDS. In AIDS related KS, it is common for disease to be in the lymph nodes. KS cells can block the flow of lymph (tissue fluid) through the lymphatic system. This build up of fluid can cause swelling in the arms or legs. This is called lymphoedema.
Lymphoedema can be very painful and uncomfortable. Unfortunately, there is no cure for this condition. But treatment can help to control and relieve it. The earlier this is picked up and treated, the easier it is to control. It is important to let your doctor know if you have any swelling that you think might be lymphoedema.
Types of Kaposi’s sarcoma
There are four types of Kaposi’s sarcoma:
- classic KS
- endemic or African KS
- transplant related KS
- AIDS related KS
This type of KS is very rare and is only found on the skin, mainly on the lower legs and feet. It is most common in older men of Mediterranean or Central and Eastern European origin. It can be a slow growing cancer and does not usually cause any problems apart from the appearance of the lesions.
You might not need treatment until the KS lesions are large and in very visible areas of the body.
Endemic or African KS
This type of KS is found in parts of Africa where HHV8 infection is common. It is faster growing than classic KS.
It affects both adults and children.
Transplant related KS
This type of KS is very rare and is most common in people with lowered immunity. This includes people who have had a stem cell or organ transplant. These people need to take drugs to stop their bodies from rejecting the new organ or stem cells. These drugs suppress the immune system. They are called immunosuppressive drugs or immunosuppressants.
AIDS related KS
KS is the most common type of tumour in people infected with HIV. It tends to grow faster than the other types. People with AIDS have a weakened immune system. This increases the risk of developing KS.
To determine if a suspicious-looking skin lesion is Kaposi’s sarcoma, your doctor will need to perform a biopsy, which involves removing a small piece of tissue for examination in a laboratory.
Tests to diagnose internal Kaposi’s sarcoma include:
- Fecal occult blood test. This test detects hidden blood in stool, which can be a sign of Kaposi’s sarcoma in the digestive tract.
- Chest X-ray. A chest X-ray may reveal abnormalities suggesting Kaposi’s sarcoma in the lung.
- Bronchoscopy. In this test, a thin tube (bronchoscope) is passed through your nose or mouth into your lungs to view their lining and take samples of abnormal areas.
- Upper endoscopy. This test uses a thin tube (endoscope) passed through your mouth to examine the esophagus, stomach and first part of your small intestine. If your doctor suspects Kaposi’s sarcoma inside any of these organs, a biopsy of the affected tissue is taken to confirm the disease.
- Colonoscopy. In this test, a thin tube (colonoscope) is passed through your rectum and advanced into your colon to examine the walls of these organs. Abnormalities suggesting Kaposi’s sarcoma in the rectum or colon can also be biopsied during colonoscopy.
Bronchoscopy is unnecessary for diagnosis of Kaposi’s sarcoma unless you have unexplained breathing problems or an abnormal chest X-ray. Similarly, unless a fecal occult blood test finds blood in your stool, you may be able to avoid upper endoscopy or colonoscopy.
The treatment for Kaposi’s sarcoma varies, depending on these factors:
- Type of disease. Historically, AIDS-related Kaposi’s sarcoma has been more serious than classic or transplant-related disease. Thanks to increasingly effective antiviral drug combinations and improved prevention of other AIDS-related infections, Kaposi’s sarcoma has become less common and less severe in people with AIDS.
- Number and location of lesions. Widespread skin lesions and internal lesions require different treatment from isolated lesions.
- Effects of the lesions. Lesions in the mouth and throat make eating difficult, while lesions in the lung can cause shortness of breath. Large lesions, particularly on the upper legs, can lead to painful swelling and difficulty moving around.
- General health. The immune system impairment that makes you vulnerable to Kaposi’s sarcoma also makes certain treatments, such as powerful chemotherapy drugs, too risky to try. The same is true if you also have another type of cancer, poorly controlled diabetes or any serious, chronic disease.
For AIDS-related Kaposi’s sarcoma, the first step in treatment is to start or switch to an antiviral drug combination that will reduce the amount of the virus that causes HIV/AIDS and increase the number of certain immune cells in your body. Sometimes, this is the only treatment needed.
When possible, people with transplant-related Kaposi’s sarcoma may be able to stop taking immune system-suppressing medication. This allows the immune system to eliminate the cancer in some cases. Switching to a different immunosuppressive medication can also bring improvement.
Treatments for small skin lesions include:
- Minor surgery (excision)
- Burning (electrodessication) or freezing (cryotherapy)
- Low-dose radiation, which is also helpful for lesions in the mouth
- Injection of the chemotherapy drug vinblastine directly into lesions
- Application of a vitamin A-like drug (retinoid)
Lesions treated in any of these ways are likely to return within a couple of years. When this happens, treatment can often be repeated.
Radiation is the usual treatment for those with multiple skin lesions. The type of radiation used and the locations of lesions being treated vary from person to person. When more than 25 lesions are present, chemotherapy with standard anti-cancer drugs may be helpful. Chemotherapy is also used to treat Kaposi’s sarcoma in the lymph nodes and digestive tract.