Nucleolar organizer regions in dysplastic and neoplastic lesions of the large bowel.

Using a silver staining technique (AgNOR technique), we have investigated the nucleolar organizer-associated proteins (NORs) in formalin-fixed paraffin embedded specimens of 20 large bowel adenocarcinomas, 10 tubular adenomas with low grade dysplasia and 10 villous adenomas with high grade dysplasia; the mean number of small NOR (SN), large NOR (LN) and total NOR (TN) was determined for each case. A significant difference (P less than 0.001) in the mean number of SN and TN was found when adenocarcinomas were compared with the adenomatous lesions; in addition, low grade and high grade dysplasia, present in tubular and villous adenomas respectively, could be clearly differentiated by this procedure. It may be suggested that the significant increase of AgNOR counts encountered in high grade dysplasia strongly supports the idea that morphological nuclear changes may reflect the severity of malignant potential of dysplasia in large bowel adenomas.