Nucleolar organizer regions in intraductal lesions associated with invasive ductal carcinoma of the breast.

To estimate cell kinetics of intraductal carcinoma present outside the invasive ductal carcinoma of the breast, an argyrophil stain for proteins associated with nucleolar organizer regions (Ag-NOR) was applied on paraffin sections of 28 breast cancers with an extensive intraductal component. The patients chosen for study were comparable to those eligible for breast-conserving surgery in our institute. The mean numbers of Ag-NOR in the nucleus were: normal duct 1.2 +/- 0.2 (mean +/- SD), normal lobule 3.1 +/- 1.2, main tumor 10.7 +/- 4.1 and intraductal lesion 7.7 +/- 2.6. A significant difference of Ag-NOR numbers was observed not only between the normal epithelium and main tumor (p < 0.01) but also between the main tumor and intraductal lesion (p < 0.01). As for intersite variation in individual cases, the Ag-NOR number of the intraductal lesion was lower than that of the main tumor in 25 out of 28 cases (89%). These results demonstrate that an intraductal lesion is less aggressive than the main tumor.