Correlation between PCNA expression and AgNOR dots in pituitary adenomas

Nucleolar organizer regions are segments of DNA associated with argyrophili c proteins (AgNORs). Our previous findings showed that the number, the area , and the intranuclear localization of AgNOR dots differ according to tumor aggressiveness and to the hormone-immunopositivity of pituitary adenomas. Proliferating cell nuclear antigen (PCNA) is a nuclear protein, whose expre ssion is correlated with cell proliferation. The aim of the present paper w as to examine PCNA-labeling indexes in pituitary adenomas and to correlate them with AgNOR dots in various immunohistochemical types of the tumors. Histological slides from 32 pituitary tumors and one normal pituitary were silver-stained and analyzed with a computerized system for microscopic imag e analysis. We found that the percentage of PCNA-positive cells did not dif fer significantly among examined groups of monohormonal adenomas. However, tumors immunopositive for cc-subunit (a-SU) showed a significantly higher ( p < 0.05) PCNA index than adenomas immunonegative for that unit. PCNA index in recurrent tumors was significantly higher than in primary adenomas. The re was a moderate positive correlation between the PCNA index and the mean area of AgNOR dots and a similar correlation between the PCNA index and the area of the biggest dot in the nucleus. The obtained results reveal that the PCNA indexes and estimated parameters of AgNOR dots differ according to tumor aggressiveness.