Kaposi's sarcoma
From Wikipedia, the free encyclopedia
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| ICD-10 | C46. |
| ICD-9 | 176 |
| ICD-O: | M9140/3 |
| OMIM | 148000 |
| DiseasesDB | 7105 |
| MedlinePlus | 000661 |
| eMedicine | med/1218 derm/203 oph/481 |
Kaposi's sarcoma (KS) is a tumor caused by Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV8). Despite its name, it is generally not considered a true sarcoma, which is a tumor arising from connective tissue. KS actually arises as a cancer of lymphatic endothelium and forms vascular channels that fill with blood cells, giving the tumor its characteristic bruise-like appearance. KS was historically very rare and found mainly in older men of Mediterranean, Jewish or African origin[1] (classic KS), or patients with severely weakened immune systems, such as after an organ transplant (immunosuppressive treatment related KS). In the early 1980s KS began to be seen in AIDS patients. This led to the belief that AIDS weakened the immune system. Kaposi's sarcoma-associated herpesvirus is responsible for all forms of KS.
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[edit] Symptoms
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 particularly 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.
[edit] 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.
[edit] 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.
Blood tests to detect antibodies against KSHV have been developed and can be used to determine if a patient is at risk for transmitting infection to his or her sexual partner, or if an organ is infected prior to transplantation.
[edit] History and theories
The disease is named after Moritz Kaposi (1837–1902), a Hungarian dermatologist who first described the symptoms in 1872. Research over the next century suggested that KS, like some other forms of cancer, might be caused by a virus or genetic factors, but no definite cause was found.
With the rise of the AIDS epidemic, KS, as initially one of the most common AIDS symptoms, was researched more intensively in hopes that it might reveal the cause of AIDS.
In 1994, Yuan Chang, Patrick S. Moore, and Ethel Cesarman at Columbia University in New York isolated genetic pieces of a virus from a KS lesion. They used representational difference analysis (a method to subtract out all of the human DNA from a sample) to isolate the viral genes. They then used these small DNA fragments as starting points to sequence the rest of the viral genome in 1996. This, the eighth human herpesvirus (HHV-8)—now known as Kaposi's sarcoma-associated herpesvirus (KSHV)—has since been found in all KS lesions tested, and is considered the cause of the disease. KSHV is a unique human tumor virus that has incorporated cellular genes that cause tumors into its genome ("molecular piracy"); the stolen cellular genes may help the virus escape from the immune system, but in doing so it also causes cells to proliferate. It is related to Epstein-Barr virus, a very common herpesvirus that can also cause human cancers.
KSHV infection does not always lead to KS; it is still unclear what other factors may be required, such as pre-existing immune system damage, or a specific interaction with HIV or other viruses. However, research in Africa has shown that even in the absence of HIV/AIDS, KS is more common in men than women although KSHV infection is equal between both sexes. This suggests that sex hormones may either protect from or predispose to KS in persons infected with the virus.
[edit] KS Awareness
In AIDS patients, Kaposi's sarcoma is considered an opportunistic infection, i.e., a disease that is able to gain a foothold in the body because the immune system has been weakened. With the rise of AIDS in Africa, where KSHV is widespread, KS has become the most frequently reported cancer in some countries, such as Zimbabwe.
Because of their highly visible nature, external lesions are sometimes the presenting symptom of AIDS. Kaposi's sarcoma entered the awareness of the general public with the release of the film Philadelphia, in which the main character was fired after his employers found out he was HIV-positive due to visible lesions. Unfortunately, by the time KS lesions appear, it is likely that the immune system has already been severely weakened.
[edit] References
- Kaposi, M. 1872. Idiopathisches multiples Pigmentsarkom der Haut. Arch. Dermatol. Syph. 4:265-273.
- Antman K, Chang Y. Kaposi's sarcoma. New Engl J Med 2000;342(14):1027-38
- Chang Y, Cesarman E, Pessin M, et al. Identification of herpesvirus-like DNA sequences in AIDS-associated Kaposi's sarcoma. Science 1994;266:1865-9.
- Yarchoan R, Tosato G, Little RF. Therapy insight: AIDS-related malignancies - the influence of antiviral therapy on pathogenesis and management. Nature Clin Prac Oncology 2005;2(8):406-15.
