Kaposi's sarcoma (KS) is a disease in which cancer cells are found in the tissues under the skin or mucous membranes that line the mouth, nose, and anus.
KS causes red or purple patches (lesions) on the skin and/or mucous membranes and spreads to other organs in the body, such as the lungs, liver, or intestinal tract.
Kaposi's sarcoma consists of characteristic skin lesions that range from flat to raised purple plaques. These tumors have a rich network of small blood vessels, and red blood cells moving slowly through these channels lose their oxygen, changing from red to blue. The mixture of red and blue cells gives the KS lesion a characteristic purple color.
There are several forms of KS, based on cause rather than appearance. The "classic" Kaposi's sarcoma, found mainly in Mediterranean males and mid-European Jews, has always been rare. In the 1950s a large number of cases were found in Africa, and the incidence has dramatically increased since then. KS was later found to be a common result of an alteration of body immunity.
There are two circumstances under which this alteration takes place. The first is when depression of the immune system is part of some treatment, for example in kidney or other organ transplants. To prevent the foreign organ from being rejected, powerful drugs are given to shut down the immune system.
The second circumstance is associated with Acquired Immune Deficiency Syndrome (AIDS).
Types Of Tumors
KS tumors are divided into three groups, based on appearance, with much overlap.
Nodular lesions are of varying size and thickness. They are purple and will at times have a halo of brown or yellow pigment around them.
Infiltrating lesions may be quite large, may be raised, or grow downward beneath the skin.
Lymphatic lesions can mimic other causes of swollen lymph nodes and may require a biopsy to rule out infection.
Under the microscope, all three types of KS appear similar. But three sub-types have been identified, all of which are treated much the same. The spindle cell variety is the slowest growing, the anaplastic is the most aggressive, and the mixed cell has a somewhat intermediate growth rate.
The epidemic KS, occurring as a disease that accompanies AIDS, is thought to have a cause - the virus named HIV (Human Immunodeficiency Virus). If given a blood test for HIV, nearly all patients with epidemic KS will show evidence of being infected.
Various ideas have been advanced to explain how this virus causes KS. One theory is that it causes a normal cell to become malignant either directly or by initiating a chain of events. Various agents that may be involved in such a change have been identified.
Yet another idea has to do with the body's T cells, some of which hunt for malignant cells that have developed spontaneously and kill them off before they can become cancers. The T cell is known to be infected with the virus and cannot kill the malignant cells.
There are no general symptoms of early KS. In the epidemic form, KS may be the first sign of AIDS, or, the first lesion may follow an illness of months or years. During this time, the patient may have had non-specific symptoms such as fever, weight loss and sweating. Possibly there were other illnesses, such as lymphoma or tuberculosis, before the first KS lesion developed.
Once the disease occurs, symptoms relate to the site of involvement. Early and more advanced skin lesions are usually only mildly uncomfortable, although painful ulcers may occur.
Lesions in the gastrointestinal tract are very common but rarely cause significant symptoms. Early lesions in the lung have no symptoms either, but severe lung involvement produces a profound air hunger.
KS is not considered curable. Neither surgical removal of the first-detected lesion nor obtaining a complete remission of multiple sites with chemotherapy or other techniques results in cure. Long-term survival does occur both with or without treatment, however.
Survival in classic KS is usually years and sometimes decades. Some patients with AIDS-related KS are still alive after 10 years, though most survive only a few years and treatment decisions are usually aimed at palliation.
All forms of KS are sensitive to radiation therapy. Radiation is especially useful for lesions that are cosmetically disturbing, painful, involve the mouth extensively, block lymphatics, bleed, or protrude from the skin. Response rates are quite high and treatment is well tolerated.
Chemotherapy can be used in treatment but there is concern that aggressive treatment might further depress the immune system. The disease does respond to chemotherapy, both with single agents and combinations of drugs.
KS is one of the few tumors that responds to local injections of chemotherapy. Many anticancer drugs cause intense local damage if they are accidentally injected into tissue. This undesirable effect has been used in a positive way to treat skin lesions.
Biological therapy involves immunologic treatment of KS primarily with the interferons, mainly alpha. Other agents, especially interleukin-2 are being studied.