Semiautomatic quantification of silver-stained nucleolar organizer regions in tissue sections and cellular smears

Silver staining of nucleoli reveals argyrophilic proteins associated with nucleolar organizer region (Ag-NOR) proteins. Argyrophilic components appear as dots about 1 micron in diameter dispersed throughout the nucleolus (Ag-NOR dots). The count of Ag-NOR dots is a useful index for improving the cancer diagnosis and determination of prognosis. Here we describe software developed on a medium-cost image analyzer in order to evaluate the mean area of NORs and their number relative to an internal reference, the number and areas of clusters of NORs and the area of the nucleus. Statistical analysis of the data was performed during counting. The first application concerned counting NOR dots during mitosis in cell imprints; those counts were 2.3, 15.3 and 55.56 for the metaphase, telophase and interphase, respectively (relative to unitary dots of metaphase cells). In the second application we demonstrated a significant difference in NOR numbers between two groups of prostatic cancers with good and poor prognoses (6.05 +/- 2.79 SD and 7.96 +/- 3.01, respectively; with Student's t test, = 1.999; P = .05).