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

There have been few reports of neoplasia in hyenas to date. In this report, we describe a captive adult female spotted hyena (<i>Crocuta crocuta</i>) 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.