ABSTRACT
Neuroendocrine cells are of the peptide and amine secreting cells and because of endodermal origin, exist in respiratory and gastrointestinal system. The report confirms the presence of a tumor using immunohistochemical methods. A hepatic mass was detected in a 10-year-old male mixed-breed dog which was referred with clinical history of frequent vomiting, anorexia, lethargy and syncope. Biochemical and hematological abnormalities included elevation of ALT and AST levels, leukocytosis and anemia. Radiographically the large hepatic mass and multifocal metastatic nodular areas in the other organs were observed. At necropsy the liver had a multilobulated firm mass involving whole caudate lobe of the liver. On the cut section, the tumor was grey sanguineous with hemorrhagic surface and numerous necrotic foci. Microscopically, there were unencapsulated, highly cellular neoplastic proliferations with few hemorrhagic foci in the liver that had a trabecular pattern to Rosette formation which were separated by a fibrovascularstroma. The neoplastic cells were round to oval, with granular eosinophilic cytoplasm and hyperchromatic nuclei. Metastases were observed in lungs, kidneys, mesenteric lymph nodes and even in the arteries of the tunica albuginae of the testes. Immunohistochemically, neoplastic cells were immunoreactive for NSE and S100 protein. They were negative for CEA, Chromogranine A, CD34, AE1/AE3, CK20 and Hepatic Antigen [HA]. Negative CEA, CK20, CD34 and HA disproved the probability for collangiocarcinoma, metastatic carcinoma, hematopoietic and vascular origin and hepatocellular carcinoma of this tumor respectively. Immunohistochemical demonstration of NSE and S100 protein supported the diagnosis of the Carcinoid like. However, negative reaction for Chromogranine A does not disprove neuroendocrine carcinoma diagnosis