Reactive mesothelial hyperplasia mimicking mesothelioma in an African green monkey (Chlorocebus aethiops)

Our plain-English summary of Reactive mesothelial hyperplasia mimicking mesothelioma in an African green monkey (Chlorocebus aethiops), by R. Plesker, K. Köhler, S. von Gerlach, et al (Primate Biology, 2020).

The study

• Authors: R. Plesker, K. Köhler, S. von Gerlach, K. Boller, M. Vogt, I.S. Feder
• Journal: Primate Biology
• Published: 2020;7(1):5-12
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A spontaneous reactive mesothelial hyperplasia occurred in a female, 15.7-year-old African green monkey (grivet; Chlorocebus aethiops). At necropsy, massive effusions were found in the abdomen, the thorax, and the pericardium. Additionally, multiple small, beige-gray nodules were detected on the serosal surfaces of the abdominal organs. Histopathologically, the mesothelial cells resembled the epithelioid subtype of a mesothelioma, but no infiltrative or invasive growth could be demonstrated. The mesothelial cells on the thoracis, liver, and intestinal serosa were accompanied by chronic serositis. Mesothelial cells expressed cytokeratin, vimentin, calretinin, desmin, Wilms Tumor 1 (WT-1) protein, and epithelial membrane antigen (EMA). Cells were negative for carcinoembryonic antigen (CEA), cluster of differentiation 15 (CD15), and podoplanin. Ultrastructurally, cells revealed a moderate amount of microvilli of medium length, perinuclear tonofilament bundles, and long desmosomes. In fluorescence in situ hybridization (FISH) for the detection of characteristic gene loss (p16; CDKN2A), NF2, and MTAP, no deletions were detected. No asbestos fibers and no presence of Simian virus 40 antigen (SV40) could be demonstrated.

Copyright: © 2020 Roland Plesker et al.

In plain English

This short communication reported one animal: a female, 15.7-year-old African green monkey (grivet). It was born and housed at the Paul-Ehrlich-Institut in Langen, Germany, used for experimental blood collection, and found dead. At necropsy, fluid had collected in the abdomen (700 mL), the chest (about 300 mL) and the sac around the heart (about 50 mL). Many small beige-gray nodules, up to 0.5 mm, lay on the surfaces of the abdominal organs. Under the microscope, the lining (mesothelial) cells resembled the epithelioid subtype of mesothelioma, but they did not show tissue invasion. They rested on chronically inflamed connective tissue. Staining patterns indicated the cells were mesothelial in origin. Genetic testing found no deletions of p16 (CDKN2A), NF2 or MTAP. No fibers were detected in lung tissue tested for asbestos, staining for SV40 virus was negative, and records showed no history of radiation. The authors concluded that this was a benign reactive mesothelial hyperplasia, a reaction to inflammation of the body linings (polyserositis), that mimicked an epithelioid mesothelioma. They stated that the cause of the inflammation could not be identified.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report (short communication) of a single animal, with necropsy, histology, immunohistochemistry, electron microscopy, genetic testing (FISH) and lung analysis for asbestos fibers
• Who was studied: one female, 15.7-year-old African green monkey (grivet; Chlorocebus aethiops), born and kept in an experimental indoor facility at the Paul-Ehrlich-Institut, Langen, Germany, and used for experimental blood collection
• Exposure: No asbestos exposure was studied or reported. The authors tested lung tissue for asbestos fibers, tested tissues for SV40 and checked the records for radiation, as possible causes of mesothelioma.
• Main results:
  • At necropsy, the monkey had 700 mL of dark-red to brown turbid fluid in the abdomen, about 300 mL of fluid in the chest and about 50 mL in the pericardial sac
  • Multiple small, round beige-gray nodules up to 0.5 mm were found on the serosa of the abdominal organs, especially the intestine
  • Mesothelial cells formed papillary projections but did not show tissue invasion
  • On the liver, intestine and especially in the thorax, the mesothelial layer rested on connective tissue infiltrated with inflammatory cells (chronic serositis)
  • No fibers were detected in lung tissue examined for asbestos
  • Mesothelial cells were positive for cytokeratin, vimentin, calretinin, desmin and WT-1, faintly reactive for EMA, and negative for CD15, CEA and podoplanin
  • Immunohistochemical testing for SV40 was negative
  • FISH found no deletion of the 9p21 locus (p16; CDKN2A), NF2 or MTAP
  • Electron microscopy showed long desmosomes, perinuclear tonofilaments and microvilli in the mesothelial cells
• The authors' conclusion: The authors concluded that the case was a reactive (benign) mesothelial hyperplasia, a reaction to polyserositis, that mimicked an epithelioid mesothelioma
• Limitations the authors state:
  • The cause of the polyserositis could not be identified, because the abdominal fluid was not investigated further and the inflammation was chronic
  • Poor preservation of the formalin-fixed, deparaffinized tissue probably prevented detection of basement membranes by electron microscopy
  • The immunohistochemical staining profile is helpful but not reliable for telling mesothelioma from benign hyperplasia

Topics

Medical terms in this study, explained in our Lexicon: Reactive Mesothelial Hyperplasia, Mesothelioma, Autopsy, Thorax, Pericardium, Serosal Surface, Mesothelial Cells, Epithelioid.

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