Nucleolar Organiser Regions in Thyroid Lesions- A Study at a Tertiary Care Hospital in South India

Abstract

BACKGROUNDThe sizes and positions of nucleoli and the proportions of their contents can vary with metabolic state, cell cycle phase and the degree of differentiation. Nucleoli aggregate and disaggregate through cell cycle. In interphase, there is complex aggregation of nucleoli (Crocker J, 1989). The principal NOR associated proteins are RNA polymerase1, Nucleolin, Numatrin, topoisomerase1, 100K protein, 80K protein, Phosphoprotein PP105 & PP135. (Crocker J, 1987). Nucleolar organiser region (NOR) associated proteins can be demonstrated by silver colloid method. Present study has been done to evaluate NOR associated proteins in 50 cases of thyroid lesions. MATERIALS AND METHODSFifty cases of thyroid lesions were selected for the study. These included follicular adenoma, follicular carcinoma, papillary carcinoma, medullary carcinoma, colloid nodule, Hurthle cell Adenoma, hyperplastic (cellular) nodule and anaplastic carcinoma. Formalin fixed paraffin embedded 3 µm sections were selected for staining. After staining, all the intranuclear AgNOR dots were counted in 100 cells two times by a single observer at 1000x magnification of oil immersion lens. RESULTSAgNOR proteins appeared as dark brown or black dots in the background of yellow stained nuclei of thyrocytes. The size, distribution and numbers of AgNOR dots in different thyroid lesions showed varied morphology and numbers. The size of AgNOR dots in small lymphocytes were taken as internal standard. There were statistically significant difference in the number of AgNOR dots of benign and malignant tumours (P value, <0.0001) CONCLUSIONAgNOR staining is a cheap and simple method which can be carried out in ordinary laboratories. Meticulous care is needed in each step of staining and counting. Advanced automated techniques could be used for meticulous quantification of NOR proteins and more research is needed in this field to apply the technique routinely in thyroid pathology.