It's a "meet cute" story as old as time: man ingests tapeworm, tapeworm grows to alarming sizes inside the man's digestive system, tapeworm begins having uncontrollable DNA errors leading to malignant cancers, man's weakened immune system allows these tapeworm tumors to spread throughout his body, everyone dies of tapeworm cancer. That's what happened to a Colombian man this month when he went to the hospital with a fever and cough, and experiencing sudden weight loss.
The doctors ran scans on the man and discovered tumors in his lungs and lymph nodes. When the doctors in Colombia did a biopsy on the tumors, they found really weird cells. Upon closer examination, the cells were rapidly multiplying and clumping just like cancer cells, but they were about 1/10 the size of human cells. Doctors also found actual, live tapeworms in the tumor, which is not usually where tapeworms live.
Freaked out, the Colombians contacted the American Center for Disease Control for help. Eventually, the mystery was solved with the help of the CDC: the tiny-celled tumors were harboring tapeworms is because the tiny-celled tumors were tapeworms (or rapidly-multiplying clusters of tapeworm cells, anyway). They didn't look like tapeworm cells anymore, but DNA tests confirmed that was what was happening.
It should be noted that the Colombian man had been HIV-positive for 10 years, but was not on any retrovirals. Normally, the human immune system fights back against parasites like tapeworms, but with the Colombian's system compromised, obviously tapeworms were allowed to grow, which raised the chances of a DNA error that could lead to tapeworm cancer, which was allowed to spread also because of the weakened immune system. Unfortunately, just 72 hours after doctors finally figured out what was happening, he died (doctors are unsure if tapeworm medication could have helped, anyway).
While this is an extremely unlikely way to die, it might not be so extreme as it sounds. Worldwide, about 75 million people are infected with the H. Nana tapeworm and 35 million live with HIV. This man's case is prompting doctors to wonder if perhaps previous examples had escaped medical notice.