A parasitic cancer or transmissible cancer is a cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 cell or cluster of cancer cells that can be transmitted from animal to animal.

They are also known as "clonally transmissible cancers".

Examples in animals

Cancer is not normally a contagious disease, but there are three known exceptions in dog

Dog

The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s, Tasmanian devil

Tasmanian Devil

The Tasmanian devil is a carnivorous marsupial of the family Dasyuridae, now found in the wild only on the Australian island state of Tasmania. The size of a small dog, it became the largest carnivorous marsupial in the world following the extinction of the thylacine in 1936...

s and Syrian hamsters. These cancers have a relatively stable genome as they are transmitted. Because of their transmission, it was initially thought that these diseases were caused by the transfer of oncovirus

Oncovirus

An oncovirus is a virus that can cause cancer. This term originated from studies of acutely-transforming retroviruses in the 1950–60s, often called oncornaviruses to denote their RNA virus origin. It now refers to any virus with a DNA or RNA genome causing cancer and is synonymous with "tumor...

es, in the manner of cervical cancer

Cervical cancer

Cervical cancer is malignant neoplasm of the cervix uteri or cervical area. One of the most common symptoms is abnormal vaginal bleeding, but in some cases there may be no obvious symptoms until the cancer is in its advanced stages...

 caused by HPV

Human papillomavirus

Human papillomavirus is a member of the papillomavirus family of viruses that is capable of infecting humans. Like all papillomaviruses, HPVs establish productive infections only in keratinocytes of the skin or mucous membranes...

.

• Devil facial tumour disease
  Devil facial tumour disease
  Devil facial tumour disease is an aggressive non-viral transmissible parasitic cancer—which likely originated in Schwann cells—that affects Tasmanian devils. The first "official case" was described in 1996, in Australia...
  
   (DFTD) is a transmissible parasitic cancer in the Tasmanian devil
  Tasmanian Devil
  The Tasmanian devil is a carnivorous marsupial of the family Dasyuridae, now found in the wild only on the Australian island state of Tasmania. The size of a small dog, it became the largest carnivorous marsupial in the world following the extinction of the thylacine in 1936...
  
  .

• Canine transmissible venereal tumor
  Canine transmissible venereal tumor
  Canine transmissible venereal tumor , also called transmissible venereal tumor , Canine transmissible venereal sarcoma , Sticker tumor and infectious sarcoma is a histiocytic tumor of the dog and other canids that mainly affects the external genitalia, and is transmitted from animal to animal...
  
   (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
  Cell culture
  Cell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...
  
   in continuous propagation.

• Contagious reticulum
  Reticular connective tissue
  Reticular connective tissue is a type of connective tissue. It has a network of reticular fibers, made of type III collagen. Reticular fibers are not unique to reticular connective tissue, but only in this type are they dominant....
  
   cell sarcoma
  Sarcoma
  A sarcoma is a cancer that arises from transformed cells in one of a number of tissues that develop from embryonic mesoderm. Thus, sarcomas include tumors of bone, cartilage, fat, muscle, vascular, and hematopoietic tissues...
  
   of the Syrian hamster, can be transmitted from one Syrian hamster to another by means of the bite of the mosquito Aedes aegypti
  Aedes aegypti
  The yellow fever mosquito, Aedes aegypti is a mosquito that can spread the dengue fever, Chikungunya and yellow fever viruses, and other diseases. The mosquito can be recognized by white markings on legs and a marking in the form of a lyre on the thorax...
  
  .

It has been suggested that animals that have undergone population bottleneck

Population bottleneck

A population bottleneck is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing....

s are at greater risks of contracting transmissible cancers.

Instances of transmission of human cancer

Transmissible cancers are rare in humans. A malignant fibrous histiocytoma

Malignant fibrous histiocytoma

Pleomorphic undifferentiated sarcoma , also undifferentiated pleomorphic sarcoma and previously malignant fibrous histiocytoma , is a type of soft tissue sarcoma....

was contracted from a patient by a surgeon when he injured his hand during an operation.