Proliferative activity in normal salivary gland and pleomorphic adenoma. A study by argyrophilic nucleolar organizer region (AgNOR) staining.

Proliferative activity of the structural components of normal salivary glands (27 cases) and characteristic histological areas in salivary pleomorphic adenoma (51 cases) was examined by visualization of argyrophilic nucleolar organizer regions (AgNORs). In the normal salivary gland, there were clusters of cells, each with two or three AgNOR dots, within the intercalated ducts. The mean number of AgNORs in this portion was 1.80, which was significantly higher than in the other epithelial parts. This indicates vigorous proliferative activity of the intercalated ducts, and thus the ducts may play an important role as reserve cells in neoplastic transformation. In pleomorphic adenoma, solid nests had a high AgNOR count (1.61), showing a significant difference from the tumor cells scattered in the "stroma". Thus the decrease in proliferative ability might occur concurrently with formation of the extracellular matrix.