Nucleolar organiser regions in pituitary adenomas.

Nucleolar organiser regions have been identified by a silver-staining technique (AgNORs) and quantified in paraffin sections of normal foetal and adult pituitary gland and in a series of 35 pituitary adenomas, which included all the main types. In the adult pituitary there were 1.45 +/- 0.07 (mean +/- SEM) AgNORs per cell and in the foetal gland 2.94 +/- 0.37. The overall values for the adenomas were 1.98 +/- 0.08. Macroadenomas had significantly higher numbers (2.18 +/- 0.09) than microadenomas (1.69 +/- 0.11). Of the hormonally active tumours, corticotroph adenomas had the highest value (2.18 +/- 0.15), although four out of six were microadenomas.