Nucleolar and dispersed nucleolar organiser regions (NORs) in differentiating neoplastic from atypical non-neoplastic lesions of the pancreas.

Our objective was to compare the accuracy of differentiation of pancreatic carcinoma from the benign ductular aggregation of chronic pancreatitis using two methods, nuclear morphometric analysis and modified argyrophilic nucleolar organiser region (AgNOR) staining for nucleoli and dispersed NORs (AgNU staining). We evaluated 35 metastatic or invasive lesions of pancreatic carcinoma with low-grade atypia, 16 lesions of ductular aggregation and 12 lesions of proper epithelium. Four parameters, consisting of the size of nucleus: mean area, mean minor axis, mean major axis and mean perimeter, and two parameters of AgNu staining: mean number of AgNu-stained dots per nucleus (equal to mean number of nucleoli and dispersed NORs) and mean area of the largest AgNu-stained dot (equal to mean area of the largest nucleolus) of pancreatic carcinomas were significantly larger than those of ductular aggregations and of proper epithelia. In the discriminant analysis of four parameters of nuclear size, the discrimination of carcinomas was correct in 82.9% and that of ductular aggregations in 81.3%. Discriminant analysis by two parameters of AgNu staining showed 2 correct discrimination of lesions in 88.6% and 100%. Thus, AgNu staining was more accurate than nuclear morphometric analysis in discriminating a pancreatic carcinoma from ductular aggregation.