Invasion of Human Tissue by Cancer-Like Hymenolepis nana Cells
Larry M. Baddour, MD reviewing Muehlenbachs A et al. N Engl J Med 2015 Nov 4.
Malignant transformation of H. nana in an immunocompromised host is suggested in this case report.
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 numerous studies on the tissues.
Although cell-culture results were negative, polymerase chain reaction screening demonstrated 99% sequence homology with H. nana. Immunohistochemical analysis and in situ hybridization supported a cestode origin of the cells. Genomic sequencing and comparative analysis demonstrated H. nana variants that were consistent with mutations seen in cancer.
Citation(s):
Muehlenbachs A et al. Malignant transformation of Hymenolepis nana in a human host. N Engl J Med 2015 Nov 4; 373:1845.