A Man's Tapeworm Gets Cancer

Parasite Keeps on Giving: Man Gets Tapeworm and Tapeworm Gets Cancer

Tapeworm

Getting a tapeworm is enough to upset most people.  But when your tapeworm gets cancer ...

In 2013, a man with AIDS presented to a Brazilian hospital with, among other medical problems, a tapeworm.  After imaging showed numerous tumors throughout his body, these tumors were biopsied and found to be of tapeworm origin.  In other words, this man's tapeworm became cancerous, and these cancerous cells started spreading (metastasizing) or invading different parts of his body--both firsts in the medical literature.

  This case was reported in a November 2015 issue of the New England Journal of Medicine.

Of note, the person who was infected with the cancerous tapeworm was really sick (immunocompromised); he hadn't taken his HIV meds in years and had AIDS which was indicated by a really low white blood cell (CD4) count.  Whereas a normal immune system can fight of all kinds of infectious insults, a person with a run-down immune system is more susceptible to lots of different types of opportunistic infections including, apparently, "tapeworm cancer."  Nevertheless however remote, a tapeworm getting cancer is enough to give any person pause.

Cestodes or tapeworms are ribbon shaped and have segmented bodies.  A person becomes infected with a tapeworm after ingesting food or water contaminated with tapeworm eggs or larvae.  Once the tapeworm gets into your small intestine, it hooks onto the lining of the small intestine (intestinal villi) using its sucking cups and feeds.

The most common type of tapeworm is the dwarf tapeworm (Hymenolepis nana), which measures about 2 centimeters and is not normally seen in the stool.  Eggs of the dwarf tapeworm, however, are evidenced in the stool and used to diagnose this parasitic infection. 

The dwarf tapeworm occurs in tropical areas and affects up to 75 million people worldwide.

  In some areas, it's estimated that 25 percent of all people have tapeworms.  Unlike other types of tape worms, the dwarf tapeworm can live its entire life cycle in the human gut without need for an intermediate host. 

Children living in institutionalized settings (think orphanages in developing countries) are most likely to be infected with dwarf tapeworms.  Infection with the dwarf tapeworm rarely causes symptoms and is best prevented by good hygiene.  Infection with the dwarf tapeworm is treated with praziquantel or nitazoxanide. 

Sometimes, larval cestodes can make their way outside the gut and implant in organs and tissues outside the gut.  These cestodes are far more capable of causing serious disease than gut tapeworms.  These extraintestinal infections are treated with a drug called albendazole.

The 41-year-old Brazilian man with HIV whose tapeworm developed cancer--apparently, giving the man cancer by association--initially presented with fever, cough, weight loss and fatigue.  As previously mentioned, this man was very sick due to AIDS and had a high viral load and low CD4 count.

This patient's CT scan showed widespread swollen lymph nodes (lymphadenopathy) as well as lung, liver and adrenal nodules.  A sample of lymph node tissue was examined on biopsy and although the morphologic appearance and invasive nature of the cells indicated cancer, the cells themselves were really small--too small to be of human origin.  Moreover, the cells didn't look like tapeworm cells.

Bemused by what they saw, the Brazilian researchers contacted the CDC and sent along images and tissue samples.  After a load of tests, including immunhistochemical studies, PCR and genomic analysis, the researchers figured out that the cells were in fact cancerous cells that developed from the dwarf tapeworm.

According to the researchers, it's questionable whether the man's cancer would have responded to treatment with medications typically used to treat tapeworm.  Obviously, this hypothesis begs the question: What treatment would work on tapeworm cancer?  Maybe we'll never find out.

After 4 months of study, this Brazilian man was finally diagnosed with tapeworm cancer.  Unfortunately, the man lived only 3 more days after this diagnosis.  Shortly before his death, the man was receiving tenofovir, an HIV medication, and amphotericin, a medication used to treat histoplasmosis, an opportunistic infection which often afflicts people with AIDS.

From a clinical perspective, this finding that a man with AIDS had a tapeworm with cancer has limited generalizability.  People with AIDS have severely compromised immune systems and prone to suffer from many opportunistic infections that are rare among members of the general population.  In other words, a tapeworm cancer epidemic among healthy people is highly unlikely.  Nevertheless in the future, when a person with AIDS and a tapeworm presents with what appears to be cancer, physicians will likely remember the case of this Brazilian man and consider tapeworm cancer.

From a scientific perspective, finding a cancerous tapeworm helps us better elucidate the link between infection and cancer.  Other infections that have been linked to cancer including HPV or genital warts that can cause cervical cancer as well as hepatitis infection that can cause liver cancer; however, a parasite has never been linked to cancer before.  (For a slideshow on "6 Viruses That Lead to Cancer" click here.)

Finally, I wonder whether this case of tapeworm cancer was in fact a medical first or the first time this condition has been identified by the medical community.  Countless people in developing countries where the tapeworm is endemic die of AIDS and never receive proper medical care.  Maybe some of these people had tapeworm cancer and were never worked up for it. 

Selected Sources

Article titled "Malignant Transformation of Hymenolepis nana in a Human Host" by A. Muehlenbachs published in NEJM in 2015.  Accessed on 11/10/2015.

White A, Jr., Weller PF. Cestode Infections. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e. New York, NY: McGraw-Hill; 2015. Accessed November 12, 2015

 

 

 

 

 

 

 

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