Man dies with tumours made up of cancerous tapeworms growing inside of him

Tapeworm: Doctors were totally puzzled by the man's condition

A man has died with tumours inside him which were composed of cancerous tapeworms.

Doctors believe that the man, 41, was able to develop the rare condition because he had HIV which caused him to have a weakened immune system.

The bizarre form of the illness was eventually diagnosed by the US Centers for Disease Control and the UK's Natural History Museum, which have laid out their findings in the New England Journal of Medicine.

The patient, a Colombian, was first seen by doctors in 2013, who found that he had what initially seemed to be normal tumours across his liver, lungs and elsewhere.

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Invasion: A stock image of parasitic worms in the body

However when reanalysed by experts, the tumours - some of which were 4cm across - were found to be cancerous cells that were not human, and were much smaller.

Dr Atis Muehlenbachs, from the US Centers of Disease Control, said: "It didn't really make sense."

When analysing the condition, Dr Muehlenbachs found himself in "complete disbelief" after ruling out some initial theories.

Speaking to the BBC, he said: "This has been the most unusual case, it caused many sleepless nights.

"It should have been obvious this was cancer or an infection and not being able to tell between the two for months is unusual."

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New findings: The experts involved have published their findings in a journal

After the true nature of the condition was discovered, the patient died three days later.

The tapeworm is called Hymenolepis nana.

Dr Peter Olson from the Natural History Museum, an expert in the tapeworm, said: "There is something very special about this species.

"It is able to carry out its whole lifecycle in one host and that is absolutely unique."

More than 90% of the worm's body is designed to reproduce, releasing thousands of eggs each day into the host's gut.

But this worm itself was not cancerous.

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'Crazy': Experts had sleepless nights trying to diagnose the patient

Doctors believe that one of its eggs travelled through the lining of the man's intensities, and eventually became cancerous after mutating.

Dr Olson said: "They were dividing and proliferating out of control and that is really what defines a cancer so they had a tape worm tumour."

It is believed that 75million people have the tapeworm, but it becoming cancerous is incredibly rare.