Quantitative and morphological study of silver staining nucleolar organizer regions (AgNORs) in benign and malignant neoplasms of the canine mammary gland

Abstract

The aim of this study was try to present a new method of evaluation of the nucleolar organizer regions (NORs) being related its morphology and distribution, objectifying to verify the correlation between malignancy of tumoral cells with cellular proliferation. Twenty-nine tumors were analyzed with regard to quantitative and morphological aspects of the silver staining nucleolar organizer regions (AgNORs) and compared to four normal mammary glands used as control. The data obtained were submitted to non-parametric Kruskal-Wallis and Mann-Whitney "U" tests. The mean NORs counts of the malignant neoplastic groups tubular carcinomas (2.14 ± 0.54), papillary carcinomas (1.79 ± 0.24) and solid carcinomas (1.95 ± 0.30) showed significant difference when compared with the control group (1.16 ± 0.08). Morphological analysis of AgNORs revealed that the expression pattern of type I NORs predominate in the benign histological groups (75% of the tubular adenoma cases and 50% of the tubular carcinoma cases), whereas type II NORs pattern prevailed in the malignant behavior neoplastic groups (54,5% of the papillary carcinoma and 100% of the solid carcinoma cases). Control group showed total predominance (100% of the cases) of type IV NORs. Expression pattern of the type III NORs did not prevail in neither histological group encompassed by this study. Evaluation of AgNORs morphology reveals an useful tool for prognosis assessment of neoplastic alterations of the canine mammary gland.