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O n the Australian island of Tasmania around 20 years ago, a disfiguring, fatal cancer of the face was reported to be rapidly spreading among Tasmanian devils. The disease, known as devil facial-tumor disease, happens to be an extraordinary instance of infectious cancer. It is caused not by a virus but by the direct transfer of cancer cells from one devil to another, possibly through biting. 1 And it is not unique to devils; other examples of unusual infectious cancers have been described in species such as dogs 2 and clams. 3
These curious cases reveal that some cancer cells can “infect” receptive hosts, but they by no means indicate that all malignancies should be treated as infectious diseases. The great majority of cancers arise within the body of the host when normal cells transform and proliferate uncontrollably. Infectious cancers do, however, highlight the impartial resourcefulness of biology in both health and disease.