Thoracic papillary mesothelioma in a canine

Anatomopathologic diagnosis

Abstract

This work describes macroscopic and microscopic findings of pleural mesothelioma in a 6-y.o., , male German shepherd dog with dyspnea and weight loss for 20 days. The animal was admitted to the Veterinary Hospital of Facultad de Veterinaria Udelar, and collapsed and died during the consultation. The body was referred to the Pathology Unit for post-mortem examination. The necropsy revealed hemoperitoneum, hepatomegaly, abundant hemothorax, a large irregular mass in the mediastinum extending throughout the cavity, adhered to the parietal pleura and rib cage; was formed by multi-nodulations of few millimeters in diameter and whitish coloration, with friable consistency. In addition, hemopericardium, infiltration of the diaphragm, pericardium, and epicardium was observed. Histopathological examination of the mass and cardiac tissue identified large cuboidal to polyhedral mesothelial cells, grouped in arborizing structures with a discrete amount of connective stroma. The cells had clear cytoplasm with vacuoles, large and intensely basophilic nuclei and some of them binucleated, with prominent nucleolus, few mitoses, and marked anisokaryosis and anisocytosis, diagnosing as a papillary mesothelioma. The confirmatory diagnosis was carried out by immunohistochemistry, showing positive immunolabeling for vimentin and pan-cytokeratin in the tumor cells.