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

Our plain-English summary of Pathological Findings of Canine Idiopathic Pericarditis and Pericardial Mesotheliomas: Correlation with Clinical and Survival Data, by M. Levi, F. Parenti, L.V. Muscatello, et al (Veterinary Sciences, 2021).

The study

• Authors: M. Levi, F. Parenti, L.V. Muscatello, S. Battaia, R. Santilli, M. Perego, V. Montinaro, F. Massari, G. Sarli, B. Brunetti
• Journal: Veterinary Sciences
• Published: 2021;8(8)
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Idiopathic pericarditis (IP) and pericardial mesothelioma (PM) are causes of pericardial effusion in dogs. Pericardiectomy can be a definitive treatment in the case of idiopathic pericardial effusion or a short-term intervention for mesothelioma. The aim of the present study was to investigate which histopathologic parameters are correlated with clinical outcomes in a cohort of dogs that underwent pericardiectomy. The histopathological findings of 22 IPs and 5 PMs were compared with clinical and survival data and the immunohistochemical characterization of immune cells (CD3, CD79α, Iba1). In IP, the mesothelium was lost in 20 cases, reactive in 9, atypical in 3, and mesothelial papillary hyperplasia (MPH) was observed in 4 cases. Numerous macrophages were found in both IPs and PMs especially at the superficial layer of the pericardium. T lymphocytes were observed in mild to moderate numbers and were more numerous than B lymphocytes in both IPs and PMs. MPH was correlated with the quantity of lymphoplasmacytic infiltrate in the superficial layer, inversely related to the thickness of the pericardium, and associated with a longer overall survival. Pericardial fibrosis was present in 19 out of 22 IPs and in all mesotheliomas and was correlated with increased time from initial presentation and pericardiectomy and lymphoplasmacytic infiltrate in the deep zone. Pericardial thickness was correlated with the amount of lymphoplasmacytic and macrophagic infiltrate in the deep zone. Mesothelioma was associated with an increased number of pericardiocentesis procedures before pericardiectomy and with the presence of macrophages in the superficial pericardial layer, edema, fibrin, and hemorrhage. Disease-free interval and overall survival were significantly shorter in patients with mesothelioma compared with IP.

In plain English

This retrospective cohort study examined 27 dogs with recurrent fluid around the heart (pericardial effusion). All had part of the heart sac (pericardium) surgically removed at two Italian veterinary hospitals between 2013 and 2018. Microscopy found idiopathic pericarditis (inflammation without identified cause) in 22 dogs and pericardial mesothelioma in 5, none visible as a mass. The study did not assess asbestos exposure or establish what caused the mesotheliomas. Tissue findings were compared with clinical and survival data. Scarring (fibrosis) was found in 19 of the 22 pericarditis cases. The disease-free interval ran from surgery until fluid appeared around the lungs (clinically evident pleural effusion). Its median was 7 days with mesothelioma versus 180 days with pericarditis (the discussion gives 160), a significant difference. Median overall survival was 45 versus 467 days, also significantly shorter with mesothelioma. In pericarditis, mesothelial papillary hyperplasia showed a trend toward longer survival. The results text called it not statistically significant (p = 0.055), but a figure legend called it significant (p = 0.04). The authors concluded that prognosis was poorer with mesothelioma. They cited the retrospective design and small case numbers as limitations.

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: Retrospective cohort study of dogs treated surgically. The removed pericardium was examined under the microscope (histopathology) and by immunohistochemistry, and the findings were compared with clinical and survival data.

• Who was studied: 27 client-owned dogs with recurrent pericardial effusion that underwent pericardiectomy at two veterinary hospitals in Italy (Clinica Veterinaria Malpensa and Ospedale Veterinario I Portoni Rossi) between 2013 and 2018. 22 had idiopathic pericarditis (IP) and 5 had pericardial mesothelioma (PM). Dogs were excluded if they had other tumors, or pericarditis due to uremia and renal failure, infectious diseases or foreign bodies. Pericardia from 3 dogs without heart or lung disease served as controls.

• Exposure: Not studied. The article does not assess asbestos exposure or establish what caused the mesotheliomas. It compares tissue findings with clinical course and survival.

• Main results:

  • Fibrosis (collagen thickening of the pericardium) was the main finding in idiopathic pericarditis, present in 19 of 22 cases.
  • The disease-free interval was defined as the time from surgery to the development of clinically evident pleural effusion. It was significantly shorter in dogs with mesothelioma than in dogs with idiopathic pericarditis (p = 0.002, log-rank test).

• Mesothelioma: 16.8 ± 25 days, median 7 days.

• IP, as given in the results: 321.1 ± 338.8 days, median 180 days.

• IP, as given in the discussion: 314.1 ± 332.7 days, median 160 days.

  • Overall survival was significantly shorter in dogs with mesothelioma than in dogs with idiopathic pericarditis (p = 0.001, log-rank test).

• Mesothelioma: 48.2 ± 34.1 days, median 45 days.

• IP: 446 ± 337.1 days, median 467 days.

  • In dogs with idiopathic pericarditis, mesothelial papillary hyperplasia (MPH) showed a trend toward longer overall survival. The results text reports this as not statistically associated (p = 0.055). The Figure 4c legend instead calls the survival significantly longer (p = 0.04).
  • A higher number of pericardiocentesis procedures (fluid drainages) before surgery was correlated with a diagnosis of mesothelioma (p = 0.04, R = 0.39).
  • Pericardial thickness did not differ significantly between the pericarditis and mesothelioma cases (p = 0.89).
  • A longer time from first presentation to surgery was correlated with more fibrosis (p = 0.04, R = 0.39).

• The authors' conclusion: The authors concluded that, after pericardiectomy, prognosis was poorer in dogs with pericardial mesothelioma than in dogs with idiopathic pericarditis. They also concluded that mesothelial papillary hyperplasia was a possible prognostic indicator in idiopathic pericarditis, showing a trend toward longer survival and thinner pericardia.

• Limitations the authors state:

  • Information was collected retrospectively, and the number of cases was small.
  • The pericarditis cases may represent advanced disease, because all needed surgery. They may therefore not represent early-stage disease.
  • The scoring system needs validation in a larger caseload, and differences between observers should be considered.
  • Survival figures may be influenced by owners' decisions, for example earlier euthanasia once a mesothelioma diagnosis is known.

Topics

Medical terms in this study, explained in our Lexicon: Idiopathic, Pericardial Mesothelioma, Pericardial Effusion, Pericardiectomy, Mesothelioma, Mesothelium, Macrophage, Pericardium.

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