Kaposi's sarcoma (KS) is a type of malignant tumor of the blood vessels that develops most commonly on the skin and mucous membranes that line the mouth, nose and anus, but may also affect internal organs - particularly the lymph nodes), lungs and organs of the digestive system such as the liver, stomach and intestine. The four main types of KS are as follows:

• Classic KS is very rare and usually only occurs in older men of Mediterranean or Jewish descent, in whom there is a genetic predisposition. The tumors usually only occur on the skin, most commonly on the lower legs. Classic KS progresses slowly, sometimes over 10 to 15 years.
   
• Endemic or African KS occurs in parts of equatorial Africa. It tends to develop more rapidly than classic KS, and can affect people of all ages.
   
• AIDS-related or Epidemic KS is the commonest and most aggressively developing form, often involving both the skin and the internal organs. KS appears in 15-20% of AIDS cases. As AIDS progresses, the immune system weakens and thus the risk of developing KS increases. Recent research suggests that 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). 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. Apart from AIDS-related KS, there have been no major outbreaks of KS, and there is no evidence that KS can be casually transmitted.
   
• Immunosuppressive treatment-related KS, although rare, may occur in transplant patients receiving drugs to suppress their immune systems (immunosuppressants), so as to reduce the risk of the transplanted organ being rejected.

• Swelling of the limbs - a condition called lymphoedema - may occur if the lymph nodes are affected, which is common in AIDS-related KS. The KS cells obstruct the lymph nodes and normal 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 the presence of pulmonary (lung) lesions.
• Nausea and vomiting may indicate gastrointestinal (digestive tract) lesions.

• Biopsy: The doctor numbs the area with local anaesthetic, and takes a small sample of tissue from a lesion for examination. If the biopsy confirms the diagnosis of KS, additional tests are performed to check for signs of malignancy elsewhere in your body. These may the procedures listed below.
   
• Chest X-ray: to check for KS in the lungs and respiratory passages. Lung infections with various causes often occur in people with AIDS, so it may be difficult in these cases to ascertain whether respiratory changes shown by X-ray are caused by KS. A bronchoscopy or CT scan may be performed to confirm the diagnosis.
   
• Endoscopy: The endoscope is usually passed down your throat. You will receive a mild sedative, and local anesthetic will be sprayed on your throat to relieve discomfort. The following types of endoscopy are used to examine different parts of the body:
  
  • bronchoscopy - windpipe and lungs
  • gastroscopy - esophagus and stomach
  • esophagogastroduodenoscopy - in which a flexible tube is used to examine the esophagus, stomach and upper duodenum (upper intestine)
  • colonoscopy - lower intestine (colon). Your bowel must be empty for colonoscopy, so you will be asked to follow a specific diet and are given a bowel wash-out before the test.
  
  
• Lung function tests: if other tests show lung involvement, the patient may undergo lung function tests - blowing into a machine that takes measurements to check lung capacity and efficiency.
   
• CT scan: The scans are compiled into a detailed picture to show any signs of KS. This test is especially useful for diagnosing KS in the lymph nodes.

• Surgery: KS skin lesions - particularly small ones - may be surgically removed. Local anesthetic is injected into the skin around the lesion to numb the area. The lesion and some of the surrounding tissue is cut out, usually leaving a small scar that will fade in time. This simple procedure can be done on an out-patient basis.
  
  Skin lesions can also sometimes be removed by other methods such as cryotherapy (destroying tissue by freezing it with liquid nitrogen) or electrodesiccation (destroying tissue by drying it out with electric sparks).
   
• Radiotherapy/radiation therapy: Administered locally to kill cancer cells. This painless treatment is usually given in one dose. It may cause small skin lesions to fade completely and larger lumps to shrink, and helps reduce symptoms of internal KS, such as swelling, pain and breathlessness.
  
  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 will probably occur. The hair may grow back after treatment. Radiotherapy to tumors of the digestive system may cause nausea and vomiting. Tiredness is another common side-effect, so ensure you get sufficient rest.
   
• Chemotherapy is used if KS has spread throughout the body. Chemotherapy is a systemic treatment, because the drug travels throughout the body via the bloodstream. It may be taken orally or intravenously (injected into a vein), usually every week or fortnight.
  
  For skin KS, chemotherapy is also usually received intravenously, but may be injected directly into a skin lesion. The latter is called local or intralesional chemotherapy. It is only used for small lesions, and may be considered as an alternative to radiotherapy for sites or skin types where radiotherapy might cause unsightly darkening.
  
  If you are receiving chemotherapy, your doctor will watch for any side-effects that need treatment. Chemotherapy can affect the heart and suppress bone marrow function, causing a drop in the number of white blood cells. This makes you more vulnerable to infections and fatigue. Other side-effects include hair loss; nausea and vomiting; diarrhoea; and nerve damage in the feet, legs and hands. Chemotherapy can make your mouth sore and cause small mouth ulcers. Local chemotherapy may cause temporary skin inflammation. There are treatments to help relieve many of these side-effects: for example, you can receive a blood transfusion if you develop anemia, or antibiotics for infections.
  
  Although side-effects from chemotherapy or radiotherapy may have a negative impact on your quality of life during treatment, most will resolve gradually once the course of treatment 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 together 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. The patient will be shown how to administer these injections themselves at home. At the start of therapy, interferon can bring on flu-like symptoms, such as chills, fever, headache, fatigue and joint and muscle aches. Interleukin, a drug similar to interferon, is also sometimes used to treat KS.