Invasion of Human Tissue by Cancer-Like Hymenolepis nana Cells

Hymenolepis nana is a human tapeworm that can complete its life cycle in the small intestine; infection can proliferate for years, particularly in immunocompromised hosts. Development of extraintestinal H. nana infection in a 41-year-old HIV-infected man from Colombia prompted a multinational investigation to determine whether malignant transformation had occurred in the parasite, causing invasive disease in the host.

Initial examination of the patient revealed extensive lymphadenopathy; stool testing yielded H. nana eggs. Disease progressed despite albendazole and antiretroviral therapy, and the patient died. Because of this progression and aspects of the lymph-node and lung biopsies that suggested a malignant process, researchers performed…