Nucleolar organizer regions in adenoid cystic carcinoma of the salivary glands.

In this study of proliferative activity of adenoid cystic carcinomas (ACCs) with different histological patterns, the argyrophilic staining method of nucleolar organizer regions (AgNORs) was applied to paraffin sections from 25 tumors. Sixteen of the neoplasms showed a mixture of different histological patterns in the same section. The AgNOR numbers in the different histological pattern areas in the same tissue sections of all 16 tumors were lowest in the cribriform, intermediate in the trabecular, and highest in the solid pattern areas. The mean AgNOR number was highest in the solid pattern (3.33 +/- 0.52), and lowest in the cribriform pattern (2.12 +/- 0.43). The results show the order of proliferative activity in the different histological pattern areas of ACC, and explain the previous clinical finding that the prognosis of ACC is poorest in solid pattern ACCs. AgNOR staining appears to be a useful technique for evaluation of the proliferative activity of each histological pattern area of ACC, especially when there are different histological pattern areas in the same tissue section.