Clinical History
The 40-year-old immunocompromised patient was found to have a frontal lobe mass.
What is your diagnosis?
Correct Answer:
The image of the H&E stained tissue section shows a bradyzoite (encysted organism) of Toxoplasma gondii. This was confirmed by immunohistochemical staining (see following image) which also shows the small tachyzoites (individual free organisms). Although these organisms can be morphologically recognized on H&E, immunohistochemical staining for the organism is very useful when there is a paucity of organisms or if there is extensive necrosis making it difficult to identify the tachyzoites.
T. gondii is a very successful parasite, infecting approximately 1/3 of the worlds human population. Cats (and other felidae) are definitive hosts, while humans and a wide variety of other warm-blooded animals are intermediate hosts.
In immunocompetent humans primary infection is most commonly asymptomatic to mildly symptomatic, and establishes lifelong latent infection. Reactivation of a previously latent infection occurs in the setting of immunocompromise. Primary or reactivated Infection during pregnancy can result in severe fetal encephalitis.
Please see reference for additional information.
Reference(s) / additional reading:
Halonen SK, Weiss LM. Toxoplasmosis. Handb Clin Neurol. 2013;114:125-45. doi: 10.1016/B978-0-444-53490-3.00008-X. PMID: 23829904; PMCID: PMC4157368.
Schlüter D, Barragan A. Advances and Challenges in Understanding Cerebral Toxoplasmosis. Front Immunol. 2019 Feb 14;10:242. doi: 10.3389/fimmu.2019.00242. PMID: 30873157; PMCID:PMC6401564.
Dunay IR, Gajurel K, Dhakal R, Liesenfeld O, Montoya JG. Treatment of Toxoplasmosis: Historical Perspective, Animal Models, and Current Clinical Practice. Clin Microbiol Rev. 2018 Sep 12;31(4):e00057-17. doi: 10.1128/CMR.00057-17. PMID: 30209035; PMCID: PMC6148195.
Attias M, Teixeira DE, Benchimol M, Vommaro RC, Crepaldi PH, De Souza W. The life-cycle of Toxoplasma gondii reviewed using animations. Parasit Vectors. 2020 Nov 23;13(1):588. doi: 10.1186/s13071-020-04445-z. PMID: 33228743; PMCID: PMC7686686.
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