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| ==Pathophysiology== | | {| style="border: 0px; font-size: 90%; margin: 3px; width: 800px" |
| * Kaposi's sarcoma arises from endothelial cells, which are epithelial cells that are normally lines the interior surface of blood vessels and lymphatic vessels.
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| Kaposi's sarcoma (KS) is a tumor caused by [[Kaposi's sarcoma-associated herpesvirus|Human herpesvirus 8]] (HHV8), also known as [[Kaposi's sarcoma-associated herpesvirus]] (KSHV).
| | ! style="background: #4479BA; width: 200px;" | {{fontcolor|#FFF|Clincal Stage }} |
| | | ! style="background: #4479BA; width: 400px;" | {{fontcolor|#FFF|Histologic Features}} |
| Despite its name, it is generally not considered a true [[sarcoma]], which is a tumor arising from [[mesenchyme|mesenchymal tissue]].
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| 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.
| | '''Macular stage''' |
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| [[Image:Kaposi's sarcoma patho.jpg|thumb|200px|left|[[Micrograph]] of a Kaposi's sarcoma showing the characteristic spindle cells, high [[vascular]]ity and [[intracellular]] [[hyaline]] globs. [[H&E stain]].]]
| | * Thin vessel wall |
| | | * Angulated vessels throughout dermis |
| KS lesions contain tumor [[cell (biology)|cells]] with a characteristic abnormal elongated shape, called ''spindle cells''.
| | * Plasma cell and hemosiderin infiltrates |
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| The tumor is highly [[Blood vessel|vascular]], containing abnormally dense and irregular blood vessels, which leak red blood cells into the surrounding tissue and give the tumor its dark color.
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| | | '''Patch stage''' |
| [[Inflammation]] around the tumor may produce swelling and pain.
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| | | * Angulated lumina that dissect dermal collagen |
| Although KS may be suspected from the appearance of lesions and the patient's risk factors, definite diagnosis can be made only by [[biopsy]] and microscopic examination, which will show the presence of spindle cells.
| | * Premonitory sign |
| | | * Spindle cells surround angiomatoid vascular spaces filled with RBC |
| Detection of the KSHV protein [[LANA]] in tumor cells confirms the diagnosis.
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| | | '''Tumor stage''' |
| ===Transmission===
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| In Europe and North America, KSHV is transmitted through saliva. Thus, kissing is a theoretical risk factor for transmission. Higher rates of transmission among gay and bisexual men have been attributed to "deep kissing" sexual partners with KSHV.<ref>http://content.nejm.org/cgi/content/abstract/343/19/1369</ref> Another alternative theory suggests that use of saliva as a sexual lubricant might be a major mode for transmission. Prudent advice is to use commercial lubricants when needed and avoid deep kissing with partners with KSHV infection or whose status is unknown.
| | * Solid nodules |
| | | * The presence of spindle cells and red blood cells in a slit-like lumina |
| KSHV is transmissible during organ transplantation
| | * Abscence of cellular atypia or mitotic activity |
| <ref name="bloodjournal.hematologylibrary.org">http://bloodjournal.hematologylibrary.org/cgi/content/full/90/7/2826</ref> and to a lesser extent through blood transfusion.<ref>http://content.nejm.org/cgi/content/abstract/355/13/1331</ref> Testing for the virus before these procedures is likely to effectively limit [[iatrogenic]] transmission.
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| They used [[representational difference analysis]] (a method to subtract out all of the human DNA from a sample) to isolate the viral genes.
| | '''Lymphangioma-like variant''' |
| They then used these small DNA fragments as starting points to sequence the rest of the viral genome in 1996.
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| This, the eighth human herpes virus (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.
| | * Thin walled, angulated vessels |
| | | * Absence of red blood cells |
| KSHV is a unique human tumor virus that has incorporated cellular genes that cause tumors into its genome ("molecular piracy");
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| the stolen cellular genes may help the virus escape from the immune system, but in doing so it also causes cells to proliferate.
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| It is related to [[Epstein-Barr virus]], a very common herpes virus that can also cause human cancers.
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