This study describes the anatomopathological and immunohistochemical findings of a canine peritoneal mesothelioma. A nine-year-old male Setter with no clinical history was submitted to necropsy. Macroscopically, many whitish firm nodules ranging from a few milimeters to 2cm in diameter were found in the abdominal cavity. These nodules had a smooth surface and were scattered throughout the parietal and visceral peritoneum and also on the spermatic cord. Histologically, neoplastic mesothelial cell groups surrounded by a large amount of fibrous connective tissue were observed. These cells were either spindle shaped or epithelioid with a vacuolated cytoplasm and oval nuclei with granular chromatin and prominent nucleoli. Many cystic spaces lined by a single or many layers of flat or columnar neoplastic cells were observed. These cysts were filled with PAS-positive eosinophilic material. Cartilaginous metaplasia and necrosis were also detected. The mesothelial cells showed intense and diffuse immunoreactivity for protein S100 and cytokeratin (AE1/AE3), however there were no reactivity for vimentin and CEA and the reactivity for human mesothelial anti-cell (HBME-1) was strong and multifocal. Based on the histopathological and immunohistochemical findings the diagnosis of sclerosing peritoneal mesothelioma was made.
Dog; mesothelioma; peritoneum; immunohistochemistry
