Quantification of nucleolar organizer regions in skin tumors

Background: Nucleolar organizer regions (NORs) have recently attracted much attention because of claims that their frequency within nuclei is significantly higher in malignant cells than in normal, reactive, or benign neoplastic cells. Objective: The purpose of this paper is to analyze a method allowing selection of the best morphometric criterion for quantifying AgNOR proteins under conventional observation conditions by light microscopy. Method: We tried to investigate the various parameters including NORs counting in cutaneous tumors using image analysis system. Results: There were significant differences in mean nucleus area per a AgNOR, nucleus area between the benign and potentially malignant group. But the conventional counting of AgNORs is not able to differentiate between the two groups. We could discriminate squamous cell carcinoma from Bowen's disease using parameters of mean ratio of AgNORs area per nucleus area, mean ratio of greatest AgNORs area per nucleus area, coefficient of variation (CV) of nucleus area, and mean area of largest AgNORs. In squamous cell carcinoma and keratoacanthoma, CV of nucleus area has shown a significant difference. Conclusion: Study of AgNORs using image analysis system is a useful tool for the diagnosis of cutaneous tumors.