Nucleolar organizer regions in endometriosis, atypical endometriosis, and clear cell and endometrioid carcinomas

Nucleolar Organizer Regions (NORs) code for ribosomal RNA and are thought to be an accurate representation of the percentage of cells in S-phase. NORs are associated with nonhistone nucleoproteins, which can be stained with silver (AgNORs). An increased number of AgNORs has been observed in many malignancies. AgNORs were counted in three groups of patients with endometriosis (Group I), atypical endometriosis (Group II), and clear cell or endometrioid carcinomas (Group III) to assess the malignant potential of atypical endometriosis. Each group consisted of 10 patients. Mean AgNOR counts were 5.83 (Group I), 7.68 (Group II), and 15.42 (Group III). The results were analyzed and were significantly different for all groups (P less than 0.05 for Groups I and II, P less than 0.02 for Groups II and III, and P less than 0.01 for Groups I and III). A critical AgNOR count of 8.20 was calculated utilizing AgNOR counts from Group I. Three of the four patients with AgNORs greater than 8.20 and atypical endometriosis developed a malignancy. AgNOR counts provide useful information, represent an inexpensive test which can be obtained from fixed tissue, and may aid in clinical management of patients with atypical endometriosis.