Predictive assessment of micro RNA expression level and number of nucleolar organizer regions with follicular thyroid tumor of undetermined malignant potential

Abstract

Introduction This article presents the current views on follicular thyroid tumor of undetermined malignant potential (FTUMP) taking into account the principles of WHO classification. Molecular genetic study with identification of mutation of some genes as well as determination of expression level of some microRNAs are given as methods for detection of potential predictors of oncodiagnostics. It was shown that the state of nucleus organizer regions is a marker of cell proliferation rate.The aim of the investigation was to estimate prognostic significance of expression level of some microRNAs and amount of regions of the nucleus organizers in the thyroid tissue at FTUMP to objectify approaches to development of adequate surgical tactics.Materials and methods Profile, microRNA expression level by real time PCR and regions of the nucleus organizers were studied in 98 cases of FTUMP which made up 4.75% of all cases of thyroid tumors operated on during four years.Results In 29 (29.6%) cases the spectrum of microRNA typical for malignant neoplasms was registered in the tissue of the FTUMP. In the remaining 69 (70.4%) cases out of 98 observations the spectrum and the expression level of microRNA corresponded to the follicular adenoma. Statistically significant differences in the average number of AgNORs and correlation between the cell area and the number of AgNORs granules were found within the formed subgroups.Discussion Increase of the mean number of AgNORs and the ratio of the nucleus area to the number of silver nitrate granules in the 2nd subgroup in comparison with the 1st one, as well as the appearance of the type II cells testifies to the appearance of the proliferating tumor cells in a new tumor growth and can be considered as prognostic criteria of tumor malignization. These results correlate with the findings of molecular-genetic study. Conclusion The data of the literature and the results obtained by studying the profile and the expression level of a number of microRNAs, morphometric characteristics and counting of thyrocyte nucleus organizer regions may serve as additional criteria for evaluation of the proliferative activity of the follicular epithelium in thyroid neoplasms, in particular to clarify the malignancy potential. Preoperatively diagnosed conditionally malignant FTUMP will allow to justify the necessity and amount of surgical intervention, and if a complex of criteria of conditionally benign FTUMP is revealed, to stick to the waiting tactics and refuse surgical intervention.