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:
KS was previously a very rare disease, found primarily in elderly Mediterranean and Jewish men, organ transplant patients, and men in parts of equatorial Africa. With the advent of the AIDS epidemic in the 1980s, doctors began to see more cases of the disease in homosexual men with AIDS. AIDS-related KS is the commonest and most aggressively developing type of KS. All forms of KS occur more commonly in men: about eight or nine men get KS for every woman who contracts the disease.
The exact cause of KS is not yet fully understood. In immunocompromised patients, however, KS is caused by co-infection with human herpes virus 8, previously called Kaposi's sarcoma associated virus.
Although KS usually begins on the skin, it can develop in several parts of the body simultaneously – unlike most cancers, which start at one site and may then spread to others.
KS on the skin appears as a small, flat area or lump that is painless and does not itch. These growths, called lesions, are usually the first signs of KS, and range in color from brown to reddish-purple. (They typically look red or purple on pale skin, and bluish, brownish or black on dark skin.) They may resemble bruises, but do not blanche (turn pale) when you apply pressure to 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, tumor growth is slow; in others, growth is rapid with new lesions appearing every week or fortnight. As the lesions progress, they grow together and form a larger tumor.
Symptoms and signs of internal KS depend on the site of the tumor:
If there are signs of KS, a doctor should examine the entire skin surface and lymph nodes. He or she will also most likely perform a general examination and a blood test. KS may be suspected if the characteristic skin lesions are present, but a biopsy (tissue sample) is usually necessary 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:
Early or slow-growing KS, involving only a few small skin lesions, may not require treatment. However, if the lesions are unsightly and causing distress, the patient may prefer to have them treated. Cosmetic products are also available to make lesions less noticeable.
Treatment options depend on different factors, including the type of KS, the age and general health of the patient, and the location and extent of the tumors. There are four main types of treatment for KS: surgery (removing the tumors), chemotherapy (using drugs to kill cancer cells), radiation therapy (using high-energy rays to kill cancer cells), and biological or immunotherapy (using the body's immune system to fight the cancer):
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.
The outcome of KS depends on which type it is, the patient's age and general health, and whether or not they have AIDS.
KS skin lesions are not life-threatening, but KS tumors in other parts of the body can cause serious problems. Internal KS can cause blockages and internal bleeding in the digestive tract; breathing difficulties or bleeding in the lungs; and lymphedema. There is no cure for lymphedema, which can be distressing and uncomfortable, but it may be relieved through methods such as exercise and massage. Lesions in the mouth lining can cause difficulty eating.
AIDS-related KS can be fatal. The most important part of the treatment is the treatment of the HIV infection with highly active antiretroviral therapy (HAART). Treatment of the lesions without treating HIV may improve the lesions, but does not necessarily improve survival, and tumors can recur even after apparently successful treatment.
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