DNA from the tapeworm was found in the man's tumour (CDC)

A man has died after a tapeworm living inside him deposited cancerous cells throughout his body.

The Colombian man had HIV, which weakened his immune system and is thought to have allowed the tapeworm to flourish.


When doctors first examined the man in 2013, the malignant cells appeared to be living in healthy tissue, much as a cancer would. The tumours were distributed across his lungs and liver, and some measured more than 4cm across.

But the cells tested negative for human proteins -- meaning they were of a non-human origin. When an autopsy was conducted the cells were found to have originated from the tapeworm. Further genome sequencing showed the tapeworm cells carried mutations associated with tumours. They were also tiny -- just a tenth of the size of a human cell.

Tumours derived from tapeworms are rare, but not unheard of, says Peter Olson, a developmental parasitologist who reported the case in the New England Journal of Medicine.

It is thought the cancer cells originated from larvae, which burrowed into the stomach and lymph nodes of the man.


Because of his compromised immune system, his body was unable to stop the invasion, and they developed into dangerous regenerative stem cells that were able to proliferate and spread the cancer.

Millions of people around the world are infected with parasitic worms at any one time. Developing cancer from such a worm is rare, though confusion around the nature and origin of the man's cancer suggests that many cases have gone undiagnosed.

Washing hands, cooking raw vegetables and thorough cooking of meat is the best way to avoid picking up a worm.