A Multistep Approach in the Cytologic Evaluation of Liver Biopsy Samples of Dogs with Hepatic Diseases

Abstract

Cytologic criteria were evaluated for their diagnostic value in liver disease in dogs. Therefore, histopathologic and cytologic examination was performed on liver biopsy samples of 73 dogs with liver diseases and 28 healthy dogs. Logistic regression analysis was used to select the measured parameters to be included in a multistep approach. With the logistic regression method, different characteristic cytologic parameters could be defined for each histopathologic diagnosis. In malignant lymphoma of the liver, the presence of large numbers of lymphoblasts with a minimum of 5% of all cells was found. Clusters of epithelial cells with several cytologic characteristics of malignancy intermixed with normal hepatocytes were indicative of metastatic carcinoma or cholangiocellular carcinoma. Liver cells in hepatocellular carcinoma were characterized by a high nucleus/cytoplasm ratio, large cell diameters, increased numbers of nucleoli per nuclei, small numbers of cytoplasmic vacuoles, and frequently, small numbers of lymphocytes. Extrahepatic cholestasis was characterized by excessive extracellular bile pigment in the form of biliary casts, an increased number of nucleoli within hepatocytes, decreased hepatic cell size, and low numbers of lymphocytes. In destructive cholangiolitis, increased numbers of neutrophils and a small mean nuclear size within hepatocytes were seen. Acute and nonspecific reactive hepatitis are diagnosed based on the presence of moderate reactive nuclear patterns, including more pronounced chromatin, prominent nucleoli, increased numbers of inflammatory cells, excluding lymphocytes, and the absence of increased numbers of bile duct cell clusters. Increased number of mast cells also was indicative of nonspecific reactive hepatitis. Important cytologic criteria for the diagnosis of liver cirrhosis, in addition to chronic hepatitis, are intracellular bile accumulation and increased numbers of bile duct cell clusters. In summary, the stepwise approach based on logistic regression presented in this study might be helpful in the objective cytologic diagnosis of hepatic diseases.