Thymoma in the dog. Case report

Abstract

A four years old Dachshund female dog was guided to the Veterinary Hospital of FMVZ-UNESP-Botucatu-SP with history of prostration, progressive weigh loss, anorexia, fatigue and drought coughs. Apathy, serous bilateral nasal discharge, intense dyspneia and lung edema were observed in the clinical exam. Thoracic X-ray showed pleural effusion and dorsal deviation of trachea and the presence of a mediastinal mass. The ultrasonography, after thoracic drainage and fine needle aspiration cytology, confirmed the presence of mediastinal mass classified as malignant neoplasm of epithelial origin. The animal died soon after the exams due to its bad clinical conditions. At necropsy mediastinal mass was located in the antero-ventral area of the thorax. It was encapsulated, with soft consistency and gray coloration with hemorragic and necrotic areas in the cut surface. The histopathology demonstrated neoplastic epithelial cells, lymphoid cells (thymocytes) with normal morphology, blood vessels of small and medium caliber, cystic formations with eosinophilic contents and Hassall corpuscles. The immunohistochemistry reaction was positive for cytokeratin AE1/AE3 and UCHL, confirming the thymoma diagnosis.