Identification of nucleolar organizer regions in non-neoplastic and neoplastic hepatocytes by the silver-staining technique.

The silver staining technique to demonstrate nucleolar organizer region (NOR)-associated proteins (AgNORs) was applied to a variety of liver tissues, including chronic persistent hepatitis (CPH), chronic active hepatitis (CAH), liver cirrhosis (LC), liver cell dysplasia (LCD), focal nodular hyperplasia (FNH), adenomatous hyperplasia (AH) and hepatocellular carcinoma (HCC). In the present study, only discrete, easily counted black dots within nuclei and silver-stained nucleolus were counted under a magnification of x400 without oil-immersion objectives. The mean AgNOR counts of HCC and LCD were significantly higher than that of normal hepatocytes, and 77% of cases of LCD and 56% of HCC had mean AgNOR counts more than 2, whereas those in CPH, CAH, LC, FNH and AH were always less than 2 and were not different from that of normal hepatocytes. Among HCC, the mean number of AgNORs increased with the grade of the tumor. However, the AgNOR counts of grade I HCC were always less than 2 and overlapped with those of normal hepatocytes and other benign categories. All cases with mean AgNOR counts of more than 2 turned out to be HCC, except LCD which exhibited characteristic histologic appearances easily distinguished from HCC. These findings suggest that AgNORs could be quantitatively useful in evaluating the grade of HCC, even under routine microscopic examination without oil-immersion objectives, and mean AgNOR counts of more than 2 per nucleus are hallmarks of HCC.