Kaposi's sarcoma (KS) is a kind of sarcoma caused by a herpesvirus infection in which cancerous cells, as well as abnormal growth of blood vessels, form solid lesions in connective tissue. KS was historically very rare and found mainly in older men of Mediterranean or African origin (classic KS) or patients with severely weakened immune systems, such as after an organ transplant (immunosuppressive treatment related KS). However, in the early 1980s a more aggressive form, epidemic KS, began to be seen in AIDS patients and was one of the first clues to the existence of the AIDS epidemic. more...
The infectious agent responsible for all forms of the disease is known as Kaposi's sarcoma-associated herpesvirus (KSHV).
KS lesions are nodules or blotches that may be red, purple, brown, or black, usually painless but sometimes painful and swollen. They most often appear under the surface of the skin or on mucous membranes, where they are only dangerous if they cause enough swelling to obstruct circulation, breathing, or eating. They may also be found in internal organs, particularly the respiratory system or gastrointestinal system; internal lesions are most commonly seen in epidemic KS, and can cause fatal bleeding.
KS can occur among transplant patients, in whom the tumor can disseminate. Stopping immunosuppression can eliminate KS but also can cause rejection of the transplanted organ.
Pathophysiology and diagnosis
KS lesions contain tumor cells with a characteristic abnormal elongated shape, called spindle cells. The tumor is highly vascular, containing abnormally dense and irregular blood vessels, which leak red blood cells into the surrounding tissue and give the tumor its dark color. Inflammation around the tumor may produce swelling and pain.
Although KS may be suspected from the appearance of lesions and the patient's risk factors, a definite diagnosis can only be made by biopsy and microscopic examination, which will show the presence of spindle cells. Detection of the viral protein LANA in tumor cells confirms the diagnosis.
Treatment and prevention
Kaposi's sarcoma is not curable, in the usual sense of the word, but it can often be effectively palliated for many years and this is the aim of treatment. In KS associated with immunodeficiency or immunosuppression, treating the cause of the immune system dysfunction can slow or stop the progression of KS. In 40% or more of patients with AIDS-associated Kaposi's sarcoma, the Kaposi lesions will shrink upon first starting highly active antiretroviral therapy (HAART). However, in a certain percentage of such patients, Kaposi's sarcoma may again grow after a number of years on HAART, especially if HIV is not completely suppressed. Patients with a few local lesions can often be treated with local measures such as radiation therapy or cryotherapy. Surgery is generally not recommended as Kaposi's sarcoma can appear in wound edges. More widespread disease, or disease affecting internal organs, is generally treated with systemic therapy with interferon alpha, liposomal anthracyclines (such as Doxil) or paclitaxel.
With the decrease in death rate among AIDS patients receiving new treatments in the 1990s, the incidence and severity of epidemic KS also decreased. However, the number of patients living with AIDS is increasing substantially in the United States, and it is possible that the number of patients with AIDS-associated Kaposi's sarcoma will again rise as these patients live longer with HIV infecton.
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