- Kaposi's sarcoma (KS) is a type of malignant tumour of the blood vessels that develops most commonly in the skin and mucous membranes, but may also affect internal organs.
- Skin tumours or lesions, which range in colour from brown to reddish-purple, are usually the first sign of KS.
- KS is associated with human herpes virus 8 (HHV-8) infection, and people with immune systems weakened by HIV/Aids are particularly vulnerable.
- Treatment for KS may involve surgery, chemotherapy, radiation therapy and immunotherapy, as well as antiretroviral treatment of the HIV infection.
What is Kaposi's sarcoma?
Kaposi's sarcoma (KS) is a malignant tumour (cancerous growth that can spread to other parts of the body), which consists of the cells that normally form blood vessels. It develops most commonly in the skin or mucous membranes lining the mouth, nose and anus. KS may also affect internal organs, particularly the lymph nodes (small structures found throughout the body that produce infection-fighting cells), lungs and digestive system.
Although KS usually begins on the skin, it can develop in several parts of the body at once.
Aids-related or epidemic KS appears in 15 - 20% of Aids cases. It often involves both the skin and internal organs. As Aids progresses, the immune system weakens and the risk of developing KS increases.
What causes KS?
Aids-related KS may be caused by a combination of immune system suppression and exposure to certain viruses, such as one form of the herpes virus, human herpes virus 8 (HHV-8), previously called Kaposi’s sarcoma associated virus. The virus is apparently sexually transmitted, because people who contract Aids through contaminated blood products or needles are far less likely to develop KS than those who acquired Aids from a sexual partner.
Symptoms and signs of KS
The first signs of KS are usually skin lesions, or growths, which appear as flat areas or lumps that are painless and do not itch. Lesions typically look red or purple on pale skin, and bluish, brownish or black on dark skin. They may resemble bruises, but do not turn pale when you press them.
Lesions often initially occur on the face, limbs and in the mouth, although any part of the skin may be affected. At first the lesions may be small, causing no problems other than cosmetic concerns. In some people, tumour growth is slow; in others, new lesions appear every week or two. As the lesions progress, they grow together and form a larger tumour.
Symptoms of internal KS depend on the tumour site:
- Swelling of the limbs (lymphoedema) may occur if KS cells obstruct the lymph nodes and lymph fluid circulation. This may lead to stretched, painful skin in the swollen areas.
- Shortness of breath, coughing and bloody sputum (substance expelled by coughing or clearing the throat) may indicate lung lesions.
- Nausea and vomiting may indicate digestive tract lesions.
How is KS diagnosed?
If there are signs of KS, your doctor will examine the entire skin surface and lymph nodes, and will most likely perform a general examination and blood test. A biopsy (tissue sample) is usually necessary to confirm the diagnosis.
How is KS treated?
Treatment decisions for KS depend on your general health, and the location and extent of the tumours. It is important to ensure that any treatment side-effects will not lead to further deterioration of your immune system. Treatment may involve the following options:
- Excision (surgical removal) of skin lesions. Local anaesthetic is injected into the skin around the lesion, which is cut out with some surrounding tissue, usually leaving a small scar that fades in time. This simple procedure can be done on an out-patient basis.
Skin lesions can sometimes be removed by other methods such as cryotherapy (destroying tissue by freezing it) or electrodesiccation (destroying tissue by drying it with electric sparks).
- Radiotherapy/ radiation therapy (using high-energy rays to kill cancer cells). This painless treatment is usually administered locally in one dose. It may fade small skin lesions and shrink larger lumps, and helps reduce symptoms of internal KS.
Radiotherapy to the skin produces minor side-effects: skin around the treated area may become red, sore or itchy, and hair loss in the affected area is likely. The hair may grow back after treatment. Radiotherapy to digestive system tumours may cause nausea and vomiting. Tiredness is another common side-effect.
- Chemotherapy (using drugs to kill cancer cells) is used if KS has spread throughout your system. The drug travels throughout the body via the bloodstream. It may be taken orally or injected, usually every week or two.
Chemotherapy for skin KS is also usually received intravenously, but may be injected directly into a lesion. This is called local or intralesional chemotherapy. It is only used for small lesions, and may be an alternative where radiotherapy might cause unsightly darkening.
Your doctor will watch for any chemotherapy side-effects, many of which can be treated. Chemotherapy can affect the heart and suppress bone marrow function, causing the number of white blood cells to decrease. This makes you more vulnerable to infections and fatigue. Other side-effects include hair loss; nausea and vomiting; diarrhoea; nerve damage; and mouth ulcers. Local chemotherapy may cause temporary skin inflammation.
Most side-effects from chemotherapy or radiotherapy resolve gradually once the treatment course is completed.
- Immunotherapy/ biological therapy/ biological response modifier therapy: uses substances made by the body or in a laboratory to boost or direct the body's immune system. This form of therapy is sometimes used to treat KS, often with another treatment such as chemotherapy. The compound used most commonly in immunotherapy is interferon, usually injected three times a week under the skin or into a lesion. At the start of therapy, interferon can cause flu-like symptoms. A similar drug, interleukin, is also sometimes used.
Early or slow-growing KS, involving only a few small skin lesions, may not require treatment. However, if you feel your lesions are unsightly and cause you distress, you may prefer to have them treated. Cosmetic products are also available to make lesions less noticeable.
What is the outcome of KS?
Aids-related KS can be fatal. The most important part of treatment is treating the HIV infection with antiretroviral therapy. Treatment of lesions without treating HIV may improve the lesions, but does not necessarily improve survival, and tumours can recur even after apparently successful treatment.
KS skin lesions are not life-threatening, but tumours in other parts of the body can cause serious problems: blockages and internal bleeding in the digestive tract; breathing difficulties or bleeding in the lungs; and lymphoedema. There is no cure for lymphoedema, but it may be relieved through methods such as exercise and massage.
What can I do to prevent KS?
Safer sexual practices may help prevent KS by reducing the risk of acquiring HHV-8 infection. Once KS is diagnosed, preserving immune function by taking anti-HIV drugs may help delay progression of the disease.
Reviewed by Dr Sithlu (Clinical Oncologist) 2008