Argyrophilic nucleolar organizer regions in human adrenocortical neoplasms

Argyrophilic nucleolar organizer regions (AgNOR) in human adrenocortical neoplasms, including five carcinomas and ten adenomas, were studied using a semi-automatic image analyzer. Both the number and total area of AgNOR per nucleus in the carcinomas were found to be statistically greater than in adenomas and control tissues. However, there were no statistically significant differences in total AgNOR area per nuclear area or in the mean area of individual AgNOR dots. The AgNOR of neoplastic and normal cells were of four morphological types: type 1 had a few dots at the periphery of the nucleus, type 2 a few dots at the center, type 3 a large round dot along with several small ones at the center, and type 4 numerous diffusely distributed polymorphic dots. Most type 3 and 4 cells were found in carcinoma cases. Type 1 cells decreased in proportion to the severity of biological malignancy. It follows from these findings that careful observation of AgNOR should facilitate the distinction of malignant from benign adrenocortical neoplasms.