Retrospective study of cytologic features of well-differentiated hepatocellular carcinoma in dogs.

BACKGROUND Cytologic diagnosis of hepatocellular carcinoma is possible when hepatocytes have prominent criteria of malignancy, but is problematic when hepatocytes have a relatively normal morphologic appearance. OBJECTIVES The aim of this study was to determine the cytologic features of histologically confirmed well-differentiated hepatocellular carcinomas (WD-HCC) in dogs to develop reasonable criteria for an accurate diagnosis when obvious criteria of malignancy in hepatocytes are lacking. METHODS Slides of ultrasound-guided fine-needle aspirates of 15 histologically confirmed WD-HCC in dogs were evaluated retrospectively using a scoring system (0-3) established for 33 cytologic features. For comparison, 15 cytologic samples of non-nodular non-neoplastic liver were evaluated using the same criteria. Statistical analysis included multiple hypothesis testing using the Benjamini-Hochberg method or false discovery rate control to correct for multiple comparisons. RESULTS The most significant and useful cytologic features in the diagnosis of canine WD-HCC were dissociation of hepatocytes, acinar or palisading arrangements of neoplastic cells, and the presence of naked nuclei and capillaries, together with mild anisocytosis, anisokaryosis, multinuclearity, and increased N:C ratios. CONCLUSIONS Cytologic features of canine WD-HCC were determined. Further studies are warranted to compare these cytologic criteria among WD-HCC, hepatomas, and hyperplastic nodules and to examine co-variance of the 33 cytologic features.