CDC links parasite cancer cells to human tumors

As if parasites weren’t worrisome enough, researchers recently discovered that cancer cells in a common tapeworm can cause cancer-like tumors in humans.

Scientists at the Centers for Disease Control and Prevention found cancer cells originating in the dwarf tapeworm may take root in people with weakened immune systems and cause tumors.

Researchers worry that other similar cases could be misdiagnosed as human cancer, especially in less-developed countries where the dwarf tapeworm and immune-suppressing illnesses (such as HIV) are widespread.

“We were amazed when we found this new type of disease – tapeworms growing inside a person essentially getting cancer that spreads to the person, causing tumors,” said Dr. Atis Muehlenbachs, staff pathologist at the and lead study author, in a news release.

“We think this type of event is rare. However, this tapeworm is found worldwide and millions of people globally suffer from conditions like HIV that weaken their immune system,” Muehlenbachs said. “So there may be more cases that are unrecognized. It’s definitely an area that deserves more study.”

In 2013, doctors in Colombia asked the CDC to diagnose odd biopsies of lung tumors and lymph nodes from a 41-year-old man with HIV. The tumors looked similar to a human cancer, but initial CDC lab studies revealed the cancer-like cells were not human.

The researchers performed dozens of tests before eventually discovering DNA from dwarf tapeworms in the man’s tumor. The man died 72 hours later.

Researchers are unsure how to treat people in similar situations.

Drugs to treat tapeworm infections may not be effective against tapeworm cancer cells in people. And it’s unclear whether human cancer treatments would help, though researchers suspect they would be beneficial.

The dwarf tapeworm infects up to 75 million people at any given time, making it the most common tapeworm infection in humans.

Marissa Harshman

Marissa Harshman

I'm the health reporter for The Columbian newspaper in Vancouver, Wash. I started at The Columbian -- my hometown newspaper -- in September 2009. Reach me at or 360-735-4546.

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