Histopathological and Immunohistochemical Study of a Hepatic Carcinoid in a Cat

Abstract

Histological and immunohistochemical examination of a feline hepatic neoplasm was conducted. A Japanese domestic neutered female cat, 5 years and 6 months old, 4.8kg in weight, and suffering from anorexia, depression, and vomiting was evaluated. The presence of a tumor in the right lateral lobe of the liver was revealed by an ultrasound examination and elevated liver enzymes on the blood examination. A suspected neoplasm was subsequently surgically removed. The mass was located in the lateral right hepatic lobe and was solid, dark reddish, rich in blood, and 3.5 × 2.5 × 2.0 cm in size. Microscopic examination revealed the cord and ductal structure of the neoplasm cells. Grimelius staining revealed positive granules in the cytoplasm, particularly concentrated toward the inside of the duct. Based on these findings, the tumor was diagnosed as a hepatic carcinoid, which is rare in cats. Immunohistochemical analysis showed that the tumor cells were positive for cytokeratin AE1/3, S100 protein, and NSE and negative for chromogranin A. It was suggested that feline carcinoids were not reactive with the chromogranin A antibody, which is broadly used as the marker for neuroendocrine tumors.