Usefulness of Ki-67 proliferation marker in the cytologic identification of liver tumors in dogs

BACKGROUND: Performing a biopsy is currently the best method of diagnosing liver disease. To reduce possible risk factors resulting from a biopsy, liver cytology can provide an alternative technique. The diagnostic accuracy of cytology for identifying liver tumors is, however, limited. The results of cytology might be improved by using immunochemistry for Ki-67, a proliferation marker, on liver cytology specimens. OBJECTIVES: The purpose of this study was to investigate the value of Ki-67 immunochemistry on liver cytologic specimens from dogs for identifying neoplastic diseases of the liver, by comparing the results to histologic findings. METHODS: Liver biopsy and cytology samples were obtained from 30 dogs with hepatic disease. All samples were evaluated by an anatomic pathologist and a cytopathologist. Parallel Ki-67 immunochemistry of histologic and cytologic samples was performed. The gradation of Ki-67 expression in histologic and cytologic samples was assessed. RESULTS: Cytologic specimens of liver tumors (n = 9) showed <50% Ki-67-positive cells. Twenty of 21 cases of non-neoplastic liver disease had no or few single Ki-67-positive cells. Using Ki-67, the diagnostic accuracy of cytologic evaluation was increased from 78% to 100% for malignant neoplasia. CONCLUSIONS: Based on the results of this study, the cytologic evaluation of liver together with Ki-67 immunochemistry can improve the diagnostic accuracy of cytology for liver neoplasia.