Evaluation of nucleolar organizer region (NOR) parameters in the uterine leiomyoma

Nucleolar organizer regions (NORs) were assessed in 27 women affected by uterine leiomyoma. Tissue samples obtained during surgery were silver-stained according to the method of Ploton et al. The assessed parameters were as follows: the number of argyrophylic nucleolar organizer regions (AgNORs) per nucleus, single AgNOR area, AgNOR intranuclear distribution, and AgNOR coefficient. The parameters were assessed quantitatively. It was found that the AgNOR coefficient was higher in uterine leiomyoma compared to the normal smooth muscle cells. The development of leiomyoma is associated with a marked decrease in myocyte nucleolar area, which accounts for 30% of the nucleus in the normal myometrium. With the comparable AgNOR number in the single nucleus, there were no differences in the single AgNOR granule area (1.21 microm2 +/- 0.047 and 1.11 microm2 +/- 0.025 in normal myometrium and in leiomyoma, respectively). In the normal myometrium, there was a positive correlation between nuclear area and the single AgNOR granule area, as well as between the AgNOR coefficient and the single AgNOR granule area. There was also a negative correlation between the number of granules per nucleus and their central and peripheral intranuclear distribution. The development of leiomyoma was associated with loss of all correlations observed in the control group.