Researchers at the Wellcome Trust Sanger Institute near Cambridge decoded the DNA of the cancer, which does not die when its host dies because live cancer cells can pass between the animals when they mate.
The genome of the 11,000-year-old cancer carries about 2 million mutations, many more than the 1,000 to 5,000 mutations found in most human cancers, an institute release said Friday.
"The genome of this remarkable long-lived cancer has demonstrated that, given the right conditions, cancers can continue to survive for more than 10,000 years despite the accumulation of millions of mutations," researcher Elizabeth Murchison said.
The genome of the transmissible dog cancer still harbors the genetic variants of the individual dog that first gave rise to it, the researchers said, and analysis suggests it may have resembled an Alaskan Malamute or Husky.
"We do not know why this particular individual gave rise to a transmissible cancer," Murchison said, "but it is fascinating to look back in time and reconstruct the identity of this ancient dog whose genome is still alive today in the cells of the cancer that it spawned."
Transmissible cancers are extremely rare in nature, the researchers said, as it is unusual for cancer cells to leave the bodies of their original hosts and to spread to other individuals.
"The genome of the transmissible dog cancer will help us to understand the processes that allow cancers to become transmissible," senior study author Mike Stratton said. "Although transmissible cancers are very rare, we should be prepared in case such a disease emerged in humans or other animals."
2014: The Year in Fashion [PHOTOS]
MAVEN now orbiting Mars