ARGYROPHILIC NUCLEOLAR ORGANIZER REGIONS IN COLORECTAL MALIGNANCY - APPLICATION OF TYPING BY THEIR DENSITY

Colorectal neoplasms obtained at colonoscopy were examined by argyroph ilic nucleolar organizer region (AgNOR) staining to evaluate the usefu lness of AgNOR as a discriminant for malignancy, AgNOR dots were divid ed into two kinds: 'structures' (larger and less-densely stained) corr esponding to the nucleolus, and 'units' (smaller and densely stained) presumed to be true AgNOR within the structure. The number of structur es per nucleus did not differ between the adenoma and carcinoma groups , whereas the number of units per nucleus showed a significant differe nce. However there were several cases showing an overlap between the a denoma and carcinoma groups, leading to a difficulty in deciding wheth er any given case was benign or malignant. Three types of AgNOR patter ns were categorized based on the ratio of units to structure. Type I w as defined as the unit being indistinguishable from the structure, Typ e II as each structure having one to five units, and Type III as at le ast one structure having six or more units, irrespective of total numb er of units per nucleus. The colorectal lesions in which more than hal f of the neoplastic cells showed Type III coincided well with carcinom as histologically diagnosed, with the exception of adenomas with sever e atypia, Labeling index of proliferating cell nuclear antigen (PCNA L I) differed between the adenoma and carcinoma groups with a considerab le extent of overlap, and correlated to some extent with the AgNOR val ues. These results showed that the AgNOR staining was useful for deter mining malignancy and its usefulness appeared superior to PCNA LI.