This just in from the department of weird, horrifying, and tragic news: A man in Colombia was killed by his tapeworm's cancer, reports NPR In the case study , published this week in the New England Journal of Medicine, researchers report that, in 2013, a 41-year-old man in Colombia came to the hospital with a fever, cough, and fatigue. He had lost weight over the past several months. When looking into the patient's breathing issues, the researchers found small tumors on his lungs.The patient had also been diagnosed with HIV in 2006, but this 2013 illness looked like cancer. However, there was one small issue: The tumor cellsThis, of course, presented a "diagnostic conundrum," the authors wrote.Eventually, with the help of the Centers for Disease Control and Prevention (CDC), the team figured out that the cancer cells were actually tapeworm cancer cells; the patient had parasitic tapeworms living and multiplying in his gut, causing the growth and spread of the tumors. But by then, the patient had been getting progressively worse for four months. He died only 72 hours after the researchers diagnosed his condition.So yeah, pretty awful. But it's important to keep in mind that something like this is extremely rare — not a huge new threat we need to panic about. In fact, until this happened, no one had any idea an invertebrate with cancer could pass the disease on to human hosts. And many people who have tapeworms don't even notice them. However, in someone with an already-compromised immune system (like this patient), more serious symptoms can indeed show up.That said, let's remember that we all have plenty of health-friendly tiny organisms in our systems right now; the vast majority of microscopic creatures that make their homes inside us are not evil, cancer-causing tapeworms.