Argyrophilic nucleolar organizer regions in human adrenocortical neoplasms

Argyrophilic nucleolar organizer regions in colorectal malignancy: application of typing by their density

Colorectal neoplasms obtained at colonoscopy were examined by argyrophilic nucleolar organizer region (AgNOR) staining to evaluate the usefulness of AgNOR as a discriminant for malignancy. AgNOR dots were divided into two kinds: 'structures' (larger and less-densely stained) corresponding to the nucleolus, and 'units' (smaller and densely stained) presumed to be true AgNOR within the structure. The number of structures per nucleus did not differ between the adenoma and carcinoma groups, whereas the number of units per nucleus showed a significant difference. However there were several cases showing an overlap between the adenoma and carcinoma groups, leading to a difficulty in deciding whether any given case was benign or malignant. Three types of AgNOR patterns were categorized based on the ratio of units to structure. Type I was defined as the unit being indistinguishable from the structure, Type II as each structure having one to five units, and Type III as at least one structure having six or more units, irrespective of total number of units per nucleus. The colorectal lesions in which more than half of the neoplastic cells showed Type III coincided well with carcinomas histologically diagnosed, with the exception of adenomas with severe atypia. Labeling index of proliferating cell nuclear antigen (PCNA LI) differed between the adenoma and carcinoma groups with a considerable extent of overlap, and correlated to some extent with the AgNOR values. These results showed that the AgNOR staining was useful for determining malignancy and its usefulness appeared superior to PCNA LI.

Comparative immunohistochemical studies of p53 and proliferating cell nuclear antigen expression and argyrophilic nucleolar organizer regions in pancreatic duct cell carcinomas

Thirty-eight cases of pancreatic duct cell carcinoma were examined for p53 expression and proliferating cell nuclear antigen (PCNA) by enhanced immunohistochemistry, as well as for changes in numbers of argyrophilic nucleolar organizer regions (AgNORs). Fifteen cases (39.5%) showed p53 overexpression, which tended to increase in proportion to the histopathological grading of malignancy. However, tumor stage and lymph node status were not correlated to p53 overexpression. PCNA labeling index (LI) increased with both histologically malignant grading and pathological stage, but was not correlated with lymph node status. The expression of p53 and PCNA thus did not necessarily reflect the degree of malignant development. In contrast, AgNOR number showed statistically significant correlations with these three indicators of malignancy. A comparative analysis of p53, PCNA LI and AgNOR number showed overexpression of p53 to be correlated to PCNA LI and essentially unrelated to AgNOR number. The present results thus indicate a close relation between p53 and PCNA, while AgNORs appear to be regulated separately from either of them.