[Silver-stained nucleolar organizer regions in adenoid cystic carcinoma]

The histological features of adenoid cystic carcinoma are varied. In general, the tumors are classified into 4 histological patterns: tubular, cribriform, trabecular and solid. Numerous previous reports have indicated that the tubular pattern usually represents a favorable prognosis, the solid pattern a poor prognosis and the cribriform pattern an intermediate prognosis. Therefore, the present study was undertaken to determine precisely the proliferative potential of each histological pattern of adenoid cystic carcinomas. A silver colloid technique to identify nucleolar organizer region associated protein (AgNORs) was applied to paraffin sections in a total of 16 adenoid cystic carcinomas. A morphometric analysis of highly magnified photographic images of AgNORs in light microscopic preparations was performed. Of the 16 tumors, 8 showed a mixture of different histological patterns in the same section. In comparing the AgNOR number among different histological patterns in the same section, the value was highest for the solid pattern, lowest for the cribriform pattern and intermediate for the trabecular pattern. Moreover, the mean AgNOR number also showed a stepwise increase from the cribriform pattern (2.3 +/- 0.3) through the trabecular pattern (2.9 +/- 0.2) to the solid pattern (3.3 +/- 0.6). There was a significant difference in AgNOR numbers between cribriform and trabecular and between cribriform and solid patterns. Our results indicate that the proliferative potential of histological patterns of adenoid cystic carcinoma is lowest in the cribriform, highest in the solid, and intermediate in the trabecular pattern area. The AgNOR staining technique appears to be of value in estimating the proliferative activity of adenoid cystic carcinomas.