In the first known case of its own kind, a Colombian man with HIV developed cancer-like tumors after a tapeworm – commonly found in human stomach – transmitted cancer cells in him.

The breakthrough discovery about the ability of the dwarf tapeworm, known as the hymenolepsis nana, to transfer cancer in humans was made by the Centers for Disease Control and Prevention's (CDC) "X-files" unit. The latter looks into unexplained illnesses and deaths.

CDC's discovery was based on the illness of the 41-year-old Columbian man who developed multiple tumors all over his body from a common bug found in the stomach. According to CDC, common human tapeworm is found worldwide, with nearly 75 million people carrying it at any particular time.

People get infected with tapeworm eggs when they eat something contaminated with fecal matter or mouse droppings. Mostly, the infestation yields no symptoms. However, the new case study published in the New England Journal of Medicine suggests that dwarf tapeworm might continue to reproduce itself repeatedly in some people.

Investigating into the case of the Columbian man with HIV, the researchers speculated that the weakened immune system of the man might have allowed for unchecked multiplication of the parasite inside the host. Some kind of mutation might have further triggered cancer in the tapeworms, which might have eventually infected the person as well and cause cancer-like tumors.

The presence of the dwarf tapeworm DNA in the cancer cells of the man confirmed what CDC researchers believed initially. Soon, the man died. However, the cancer did not lead to his death, but it did contribute to his decline.

The researchers are still not sure how the tapeworm cells became malignant and caused cancer in the host. However, they do believe that the condition is rare.

A 26-year-old man from California was recently told that he had only 30 minutes to live after tapeworm larvae were discovered in his brain. The larvae had formed a cyst which was blocking the circulation in his brain, resulting in severe headache.

The doctors pulled out the live tapeworm and larvae from his brain and now he lives a parasite-free life.