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A parasitic cancer or transmissible cancer is a cancer cell or cluster of cancer cells that can be transmitted from animal to animal. They are quite rare in humans and other animals. These cancers are distinct from cancers caused by infectious agents such as oncoviruses and cancer bacteria, which are more common. ==Examples in animals== Cancer is not normally a contagious disease, but there are four known exceptions in dogs, Tasmanian devils, Syrian hamsters, and soft-shell clams. These cancers have a relatively stable genome as they are transmitted.〔(Retrovirology A sexually transmitted parasitic cancer )〕 Because of their transmission, it was initially thought that these diseases were caused by the transfer of oncoviruses, in the manner of cervical cancer caused by HPV. *Devil facial tumour disease (DFTD) is a transmissible parasitic cancer in the Tasmanian devil.〔 〕 *Canine transmissible venereal tumor (CTVT) is sexually transmitted cancer in dogs. It was experimentally transplanted between dogs in 1876 by M. A. Novinsky (1841–1914). A single malignant clone of CTVT cells has colonized dogs worldwide, representing the oldest known malignant cell line in continuous propagation. *Contagious reticulum cell sarcoma of the Syrian hamster can be transmitted from one Syrian hamster to another by means of the bite of the mosquito ''Aedes aegypti''. *Soft-shell clams, ''Mya arenaria'', have been found to be vulnerable to a transmissible neoplasma of the hemolymphatic system — effectively, leukemia.〔(Selfish shellfish cells cause contagious clam cancer ), by Ed Yong, at ''National Geographic''; published April 9, 2015; retrieved April 10, 2015〕 It has been suggested that animals that have undergone population bottlenecks are at greater risks of contracting transmissible cancers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Clonally transmissible cancer」の詳細全文を読む スポンサード リンク
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