Nucleolar Organizer Regions in the Normal and Carcinomatous Epithelium of the Uterine Cervix. A Morphometric Study

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Abstract
Nonhistone nucleoproteins associated with the nucleolar organizer regions (NORs), the genes coding for the ribosomal RNA precursor, can be visualized by silver staining. The black dots (AgNORs) appearing on the nuclei are thought to reflect cell differentiation. In this study, AgNORs were counted and their area was measured and compared with the area of the nuclei in normal and carcinomatous cells of the uterine cervix. The number of AgNORs per nucleus was significantly higher in the endocervical than in the basal exocervical epithelium (p < 0.005) and in the carcinomatous epithelium, either in situ or invasive, than in both normal epithelia (p < 0.002). Individual AgNORs were significantly smaller in carcinoma in situ than in endocervical epithelium (p < 0.05) or in invasive carcinoma (p < 0.01). Significant differences were also found in the total AgNORs area per nucleus between the following groups: basal exocervical versus endocervical epithelium (p < 0.01), basal exocervical and endocervical epithelium versus invasive carcinoma (p < 0.001), and in-situ versus invasive carcinoma (p = 0.02). The conclusions are that the number and the total area of AgNORs per nucleus increase with the differentiation of the cell or with its carcinomatous transformation, but no prognostic significance can be drawn so far from our measurements.