Primary Pericardial Well-Differentiated Papillary Mesothelioma in a Spotted Hyena (Crocuta crocuta)

Our plain-English summary of Primary Pericardial Well-Differentiated Papillary Mesothelioma in a Spotted Hyena (Crocuta crocuta), by L. van der Weyden, D. Keet, N. O'Dell (Veterinary Sciences, 2025).

The study

• Authors: L. van der Weyden, D. Keet, N. O'Dell
• Journal: Veterinary Sciences
• Published: 2025;12(12)
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

There have been few reports of neoplasia in hyenas to date. In this report, we describe a captive adult female spotted hyena (Crocuta crocuta) that developed inappetence, lethargy and marked abdominal distension over a 3-day period. The hyena was chemically immobilised to allow clinical investigation of the severe symptoms; however, she died before any internal examination occurred. At necropsy, severe serosanguinous hydropericardium was evident, as well as pulmonary congestion and oedema, ascites and chronic passive congestion of the liver with mild fibrosis. Histopathological examination of the pericardial surface revealed fibrous proliferations lined by mostly a single layer of large proliferating neoplastic mesothelial cells forming papillary projections into the lumen of the pericardial sac as well as infiltration into the pericardial connective tissue, with innumerable haemosiderin-laden macrophages in places, suggestive of chronic haemorrhage. The liver revealed severe congestion and interstitial fibrosis, and the lung revealed congestion and oedema, with moderate numbers of alveolar macrophages and marked anthracosis. The diagnosis was pericardial well-differentiated papillary mesothelioma, with death under anaesthesia caused by cardiogenic shock due to pericardial mesothelioma-associated cardiac tamponade. As primary pericardial mesothelioma (PPM) is a rare tumour type for both animals and humans, and this is the first report of a PPM in a hyena, we compare the clinical findings with those seen in other species.

In plain English

This case report described one captive adult female spotted hyena, older than 16 years, at the South African National Zoological Gardens in Pretoria. Over three days she stopped eating, was lethargic and appeared bloated. She was sedated so she could be examined, but she died before the examination could be done. At necropsy, the sac around the heart contained a severe build-up of blood-tinged fluid. There was also fluid in the chest and abdomen, congestion of the lungs, and chronic congestion of the liver. Under the microscope, the outer covering of the heart showed tumour cells forming finger-like projections, and in several areas the cells grew into the tissue beneath. Staining for vimentin and cytokeratin confirmed the cells were mesothelial. The authors diagnosed primary pericardial mesothelioma, specifically well-differentiated papillary mesothelioma. They attributed death to fluid pressing on the heart, leading to heart failure and cardiogenic shock. The lungs showed marked anthracosis (carbon deposits), which the authors considered incidental. They reported no evidence of a predisposing cause such as asbestos exposure or chronic inflammation, and concluded the tumour developed spontaneously.

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 (single animal, post-mortem diagnosis)
• Who was studied: One captive adult (over 16 years) intact female spotted hyena (Crocuta crocuta) from the South African National Zoological Gardens in Pretoria; dates not given
• Exposure: No asbestos or other specific exposure was studied. The authors reported no evidence of a predisposing cause such as asbestos exposure or chronic inflammation. The only environmental finding was carbon (anthracosis) in the lung, which they considered incidental.
• Main results:
  • At necropsy, the hyena had severe blood-tinged fluid in the sac around the heart (serosanguinous hydropericardium).
  • The hyena also had moderate-to-severe congestion and fluid in the lungs, with moderate fluid in the chest (hydrothorax).
  • On microscopy, the pericardial surface showed large proliferating neoplastic mesothelial cells forming papillary projections.
  • In multiple areas, the tumour cells formed tubular structures that grew into the connective tissue of the visceral pericardium beneath.
  • The tumour cells showed nuclear atypia (abnormal-looking nuclei), and dividing cells (mitoses) were seen in most microscope fields.
  • Immunohistochemical staining for vimentin and cytokeratin was positive, which confirmed the tumour cells were mesothelial in origin.
  • The authors attributed death to the fluid around the heart pressing on it, causing congestive heart failure and finally cardiogenic shock.
  • The lungs showed marked anthracosis, which the authors considered an incidental finding not associated with mesothelioma.
• The authors' conclusion: The authors concluded that the lesion was consistent with primary pericardial mesothelioma, specifically well-differentiated papillary mesothelioma. Because they found no predisposing cause, they concluded the tumour developed spontaneously.

Topics

Medical terms in this study, explained in our Lexicon: Pericardial, Well-Differentiated Papillary Mesothelioma, Autopsy, Ascites, Fibrosis, Mesothelial Cells, Macrophage, Interstitial Fibrosis.

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• Well-differentiated papillary mesothelioma of the peritoneum is genetically defined by mutually exclusive mutations in TRAF7 and CDC42 — M. Stevers, J.T. Rabban, et al. (2019)
• Well-differentiated papillary mesothelioma of the pleura: a series of 24 cases — F. Galateau-Sallé, J.M. Vignaud, et al. (2004)
• Well-differentiated papillary mesothelioma of the female peritoneum: a clinicopathologic study of 26 cases — A. Malpica, S. Sant'Ambrogio, et al. (2012)
• Well-differentiated papillary mesothelioma with invasive foci — A. Churg, T. Allen, et al. (2014)

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