Diagnostic value of silver-stained interphasic nucleolar organizer regions in breast tumors.

Seventy-six specimens of normal breast tissue and benign and malignant breast lesions were studied to assess the mean area occupied by silver-stained proteins of the nucleolar organizer regions (MNORA) of the nucleolus. The assessment was performed with a computer-assisted image analyzer. The results indicate that only 30% of malignant lesions have a MNORA value greater than that of normal breast tissue or benign lesions. On the other hand, MNORA values of ductal carcinoma in situ were significantly greater than those of epitheliosis (papillomatosis). MNORA values were also significantly different in grade I and grade III invasive ductal carcinomas, the latter exhibiting the highest MNORA values of all the cases observed. Evaluation of MNORA values may therefore help in differentiating benign epithelial proliferations from ductal carcinomas in situ. Furthermore, because there is evidence that MNORA values are indicative of the cell duplication rate, MNORA values may ultimately be considered an objective prognostic parameter in addition to grading for invasive ductal carcinomas.