Pericardial malignant mesothelioma diagnosed in a dog by immunocytochemistry of the pericardial fluid: a case report

BackgroundPericardial effusions are one of the most common cardiac diseases in dogs. Common causes of haemorrhagic pericardial effusions include neoplasia, such as hemangiosarcoma, mesothelioma, chemodectoma, and ectopic thyroid tumours, and benign idiopathic pericardial effusion. Distinguishing among reactive mesothelial cells, malignant mesothelioma, and adenocarcinoma in body effusions is a diagnostic challenge. Therefore, the author aimed to discover whether the observed cells were reactive mesothelial, mesothelioma, or adenocarcinoma cells through immunocytochemistry using five markers (cytokeratin, vimentin, desmin, E-cadherin, and calretinin) in a canine patient.Case presentationA 2.1 kg, spayed female, 10-year-old Yorkshire Terrier dog presented to a local hospital with dyspnoea and was evaluated for pericardial effusion. The presence of pericardial fluid was confirmed, and she was referred to our hospital for further evaluation. In cytological evaluation, cells shed individually or in clusters were observed, along with numerous non-degenerative neutrophils and macrophages. The cells showed binucleation, anisocytosis, anisokaryosis, abnormal nucleoli, abundant basophilic cytoplasm, high nuclear-cytoplasmic ratio, and coarse chromatin. Large atypical multinucleate cells were also observed. Erythrophagia was observed, indicating chronic haemorrhage. Immunocytochemistry using pericardial fluid was positive for cytokeratin, vimentin, desmin, E-cadherin, and calretinin. Therefore, malignant mesothelioma was diagnosed.ConclusionsImmunocytochemistry is a very useful diagnostic technique because it can determine whether several fluorescent markers are simultaneously expressed in the same cell. Further, E-cadherin and calretinin can be used for the differential diagnosis of reactive mesothelial cells, malignant mesothelioma, and adenocarcinoma in dogs.

Automated summary

Background: Pericardial effusions are a common cardiac disease in dogs, and haemorrhagic pericardial effusions can be caused by various neoplasms and benign idiopathic pericardial effusion. This case study aimed to determine whether the observed cells in a canine patient were reactive mesothelial, mesothelioma, or adenocarcinoma cells using immunocytochemistry. Case presentation: A 10-year-old Yorkshire Terrier dog with dyspnoea and pericardial effusion was evaluated. Cytological evaluation revealed abnormal cells with characteristics of malignant mesothelioma, and immunocytochemistry confirmed the diagnosis. Conclusion: Immunocytochemistry is a valuable diagnostic technique for differentiating reactive mesothelial cells, malignant mesothelioma, and adenocarcinoma in dogs.