Pathological Findings of Canine Idiopathic Pericarditis and Pericardial Mesotheliomas: Correlation with Clinical and Survival Data

Figures

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  Figure 1. Idiopathic pericarditis, dog. (a) Pericardial sac of dog that underwent subtotal pericardiectomy, diagnosed with chronic idiopathic pericarditis. Serosa is variably thickened by multifocal-coalescing whitish areas of fibrosis; multifocal areas of hemorrhages and a focal area of gray-yellowish fibrin exudation at the inner/cardiac side of the serosa are present, 40×. (b–d) Idiopathic pericarditis, dog, H&E. (b) Mesothelial papillary hyperplasia, simple to branching papillae (arrow) lined by cuboidal mesothelial cells supported by a small axis of fibrovascular stroma infiltrated with inflammatory cells, 100×. (c) Fibrinous pericarditis, pericardium is covered by a thick mat of fibrin (asterisk) and expanded by abundant fibrosis in which multifocal aggregates of inflammatory cells are embedded, 100×. (d) Fibrous pericarditis, pericardium is replaced by abundant fibrosis (asterisk), 100×. (e) Idiopathic pericarditis, dog, Masson’s trichrome. Mature collagen is stained in blue, 100×. (f) Control pericardial tissue appeared as normal pericardium with the inner, cardiac surface covered by a single layer of flat mesothelial cells; the parietal pericardium was composed of poorly…

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  Figure 2. Mesothelioma, dog, H&E. (a) Papillary pattern of epithelioid mesothelioma. Thin papillae are visible, 100×. (b) Desmoplastic pattern of mesothelioma. Islands and cords of atypical polygonal cells are supported by abundant desmoplastic stroma, 200×. (c) Deciduoid mesothelioma. Large cells with abundant glassy eosinophilic cytoplasm, central nucleus and prominent nucleolus are present. (d) Solid mesothelioma. Multiple neoplastic emboli in lymphatic vessels (arrows), 400×.

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  Figure 3. Pericardium, dog, immunohistochemistry. (a) Idiopathic pericarditis. Pericardium is infiltrated by numerous lymphocytes CD3 positive, stained in red (AEC), 40×. (b) Idiopathic pericarditis. Few lymphocytes CD79a positive, stained in red (AEC), are present in the reactive papillae, 40×. (c) Idiopathic pericarditis. Numerous Iba1 positive macrophages, stained in brown (DAB) are present in the papillary hyperplasia of mesothelium, 100×; (d) Idiopathic pericarditis. A single layer of mesothelial cells (arrow) covering hyperplastic papillae is highlighted with pan-cytokeratin, 100×; (e) Solid mesothelioma. Multilayering of intense pan-cytokeratin positive neoplastic mesothelial cells, stained in brown (DAB), 200×. (f). Solid mesothelioma. Multiple neoplastic emboli are pan-cytokeratin positive (asterisk), 200×.

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  Figure 4. Kaplan–Meier survival curves of 22 dogs diagnosed with idiopathic pericarditis (IP) and 5 dogs with pericardial mesothelioma (ME). In each curve, the y-axis represents the survival probability. (a) Mesotheliomas have significantly shorter disease-free interval (DFI) times compared to IP (p = 0.001 log-rank test). (b) Mesotheliomas have significantly shorter overall survival (OS) times compared to IP (p = 0.0007 log-rank test). (c) Dogs diagnosed with IP showing the histologic feature of mesothelial papillary hyperplasia (MPH) have a significantly longer OS compared to IP cases lacking MPH (p = 0.04 log-rank test).