Detection of argyrophil nucleolar organizer regions (AgNORs) and proliferating cell nuclear antigen (PCNA) in epithelial skin tumours from domestic animals

Abstract

SUMMARY The objective of this study was to compare the chemical characterization of the AgNOR bodies and the immunohistochemical detection of the PCNA for differentiating benign and malignant epithelial tumours (n = 21) from various animal species (mainly dogs and cattle). Fibropapillomas / papillomas (n = 3) and fibropapillomatosis / papillomatosis (n = 3) in cattle, and perianal gland adenomas (n = 3), keracanthomas (n = 2) and epithelioma (n = 1) in dogs constituted the group of benign tumours whereas the identified malignant tumours were squamous cell carcinomas (n = 7) in cattle and in one sheep and carcinomas in dogs (n = 2). A complete AgNOR characterization with determination of the NAI (nuclear area index), the AgNAI (AgNOR area index), the AgNCI (AgNOR count index), the AgNAI/NAI (relative AgNOR area), the AgNAI/AgNCI (mean AgNOR area) and the AgNCI/NAI (AgNOR density) was performed and PCNA expression was explored in parallel by immunohistochemistry. Significant increases of AgNAI, AgNCI and AgNAI/NAI were evidenced in malignant tumours compared to benign ones whereas no significant difference of the PCNAI (numbers of PCNA positive cells) was found. Significant and positive correlations found between NAI and AgNAI or mean AgNOR area and between AgNAI and the mean AgNOR area or the relative AgNOR area in both malignant and benign tumours suggest that the AgNOR size is an important parameter for cell proliferation. By contrast, the lack of correlation between AgNCI and the relative AgNOR area and between the AgNOR density and NAI or AgNCI or AgNAI/AgNCI in malignant tumours contrary to benign tumours would be due to the under-estimation of the enumeration of the AgNOR bodies in malignant tumours mainly regrouped as AgNOR clusters.