MESOTHELIOMA IN LIONS (PANTHERA LEO) AND TIGERS (PANTHERA TIGRIS): AN ANTEMORTEM CHALLENGE

This case series describes the presentation, diagnostic, and pathologic findings for mesothelioma in ten Panthera felids at two sanctuaries. Over ten years, seven African lions (Panthera leo) and three tigers (Panthera tigris) were diagnosed with mesothelioma, with a median age of 18 years. The most common clinical signs were nonspecific (lethargy, hyporexia, weight loss) and respiratory (coughing, wheezing, dyspnea), linked to cavitary effusions. Hematology and biochemistry values did not show consistent abnormalities although elevated creatinine (4/10), neutrophilia (4/10), monocytosis (3/10), and hyperglobulinemia (4/10) were most common. Radiographs, echocardiograms, and fluid cytology identified effusion, but did not diagnose mesothelioma specifically. All pericardial fluid samples (collected from 3/10 cases) were hemorrhagic, one of which had mesothelial cells but were not definitively neoplastic and one had neoplastic cells but were not definitively mesothelial. Treatments were only palliative; therapeutic pericardiocentesis provided short-term relief for three animals. Median survival time from the onset of clinical signs was 50 (range 0-176) days. If not euthanized on presentation, cases were managed with a combination of antibiotics, antifungals, immunosuppressives, diuretics, cardiac medications, and supportive care. Cavitary effusions were identified in 8/10 of cases at necropsy, including pericardial (7/10), pleural (5/10), and peritoneal (1/10), and diagnoses were confirmed with cytokeratin and vimentin immunohistochemistry. Further research is necessary to determine true prevalence and causes of this disease in domestic and nondomestic felids and to improve antemortem diagnostic testing and treatments.