pathtalk.org is a weblog about pathology and laboratory medicine.

Compendium of Online Pathology Resources

Case of the Week 56

The following was ‘passed’ in the stool of an otherwise asymptomatic 50 year old woman. (images courtesy of Dr. Washington Winn, Fletcher Allen Health Care, VT)

Identification?

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Answer to Case of the Week 55

Answer: Rhinosporidiosis (infection with Rhinosporidium seeberi)

Congratulations to Anonymous (x 3!), Kenneth, Chris, Victor, and Santoshpath who all got this correct! The keys to the diagnosis is the clinical history (location in nasal mucosa), exposure history (India), and histopathologic features of a polypoid mass containing mature sporangia (large, thick-walled spherical structures) and smaller internal sporangiospores (daughter cells). The sporangia stain with the fungal stains Gomori methenamine silver (GMS) and periodic acid-Schiff (PAS), and may mimic the appearance of similar appearing fungi such as Coccidiodes immitis (as one viewer suggested) and Chrysosporium spp. (the agent of adiaspiromycosis). Myospherulosis, a non-infectious entity, is also in the differential diagnosis. The difference between these entities is in the size of the spherule/sporangia and the internal structures.

This organism was previously considered to be a fungus, but it is now considered to be an aquatic protistan parasite (classified under Mesomycetozoea, which includes parasites of fish and amphibians). Rhinosporidiosis is endemic in India, Sri Lanka, South America, and Africa.

Although the disease most commonly involves the mucosa of the nose, mouth, and conjunctiva, involvement of the skin, ear, genitals, and rectum has also been described. Disseminated infection has been described in 3 individuals.

Thank you all for viewing and writing in!

Case of the Week 55

Here’s a challenge for all of you: Nasal polyp removed from a 50 year old Indian man with complaints of chronic nasal obstruction. Histologic exam reveals the following:

Hematoxylin and Eosin, 40x final magnification

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Answer to Case of the Week 54

Answer: Trypomastigotes and intermediate trypomastigote/amastigote forms of Trypanosoma cruzi.

Thanks to everyone who wrote in for this case! This was, admittedly, a tricky case, since it is uncommon to see amastigote-type forms in peripheral blood. The reason these atypical forms were present is because this specimen was grown in culture and then innoculated in peripheral blood (artificial infection). Fortunately, the classic “C-shaped” trypomastigote forms with large kinetoplast were still abundant and allowed accurate identification. Although you wouldn’t expect to see a case like this in nature, this type of preparation may show up on proficiency test (since this material is typically grown in culture). Another important point of this case is that the forms on the thick smear resemble Plasmodium rings; thus, it is always important to examine BOTH the thick and thin smears!

Case of the Week 54

The following were seen on a Giemsa-stained thick blood film made from EDTA whole blood. Identification?

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