The recent report of a tapeworm infection turning into possible cancer inside a 41-year-old man sounds more like a horror movie premise than science. But it is real, and has led to questions about whether common infections, previously thought to be harmless, can turn potentially fatal.
In 2013, doctors in Medellin, Colombia, cared for a man with tumors in his lungs, adrenal glands and lymph nodes. He was HIV-positive and was not taking HIV medication, so he had a severely weakened immune system. Tissue samples showed the cancerous growths were not human.
DNA studies found that these cells were from an intestinal parasite known as dwarf tapeworm, which is found in warm climates and areas with poor sanitation. The patient ultimately died of kidney failure, but doctors suspect the tapeworm cells played a key role in his death.
This is the first known case of parasitic cells mutating to cause cancerous growths. It raises fascinating questions about the role of the immune system in cancer treatment and prevention.
It is not clear how common this condition is. For one thing, dwarf tapeworm infections are relatively unusual in developed countries with advanced water and sanitation systems.
Other parasitic infections have also been associated with cancer. For example, flatworms may lead to bile duct cancer or bladder cancer, and cause devastating disease. In such cases, cancer is thought to result from a combination of chronic inflammation and/or substances produced by the parasites that cause nearby human cells to become cancerous.