Argyrophilic nucleolar organizer region counts in exocrine pancreatic tumors.

We enumerated the number of Ag-NORs in normal pancreatic ducts and exocrine pancreatic tumors to assess their cellular activity. Our results indicate that the mean number of Ag-NOR counts increased stepwise in the following order: normal pancreatic duct (1.26), serous cystadenoma (1.27), mucinous cystadenoma (1.65), mucinous cystadenocarcinoma (2.29), noninvasive intraductal variant of mucin-producing papillary adenocarcinoma (3.16), and a common type of invasive duct cell adenocarcinoma (3.78). These results suggest that cellular proliferative activity is low in normal pancreatic ducts and serous cystadenoma, intermediate in mucinous cystadenoma, and high in mucinous cystadenocarcinoma and duct cell adenocarcinoma. In addition, mucinous cystadenocarcinoma has significantly lower Ag-NOR counts than duct cell adenocarcinoma. We conclude that a clear quantitative difference between the Ag-NOR content of tumor cells of serous cystadenoma, mucinous cystadenoma, mucinous cystadenocarcinoma, and duct cell adenocarcinoma reflects the underlying different biologic behavior (chiefly, grade of malignancy) of these lesions.