Neoplastic tapeworm cells may invade human tissue in immunocompromised hosts

1. Human disease that resembles cancer found to be from parasite-derived cancer cells of Hymenolepis nana

Evidence Rating: 4 (Below Average)    

Study Rundown: The most common tapeworm known to infect humans is Hymenolepis nana, also known as the Dwarf Tapeworm – with up to 75 million carriers estimated globally. In general, H. nana replicates in the small intestine and is not generally known to infect systems outside of the gastrointestinal tract. Atypical cellular proliferation has been documented in several tapeworm species, however, neoplastic cellular proliferation in parasitic tapeworms has not been clearly documented in the medical literature. In this case report, the researchers identify a case of an immunocompromised man with HIV and H. nana infection who demonstrated undifferentiated malignant cells from lymph-node and lung biopsies believed to be of parasite origin through molecular and genetic assays. The implications of this finding are notable as human pathology caused by neoplastic cells from parasites has not previously been described.

Click to read the study, published today in NEJM

In-Depth [case report]: In this case report, the authors describe an HIV-positive 41 year old male who was noncompliant with therapy who presented with several months of fatigue, fever, cough and weight loss and a most recent CD4 count of 28/mm3 and viral load of 70,000 copies/mm3. On further workup, the researchers found the man to have H. nana eggs in stool analysis and CT demonstrated lung, liver and adrenal nodules along with widespread lymphadenopathy. Cervical lymph node biopsy and core-needle biopsy of lung nodules showed proliferative cells with overt malignant features. However, the small cell sizes (<10 µm diameter) suggested infection from a unicellular organism. To determine the origin of the cells, the researchers performed PCR assays, IHC studies with in situ hybridization, phylogenetic analysis and genomic sequencing. Through PCR assays of cell cultures, the researchers identified a 99% sequence identity with H. nana. Phylogenetic analysis of the CO1 sequence and genomic analyses (53% coverage mapped to H. nana reference genome, 93% coverage with control) confirmed this finding.

Image: PD/CDC

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