Ivakhno I. Morphological prognostic criteria of papillary thyroid microcarcinomas.

Thesis is devoted to improvement of the morphological diagnosis of papillary thyroid microcarcinomas (PTM) by studying the morphological and molecular features which determine the clinical course and prognosis of the disease. The basis of morphological and molecular studies thesis have made histological specimens of 181 patients had surgery for PTM. It was found that thyroid microcarcinomas make up 18.9 % of thyroid malignancies. In thesis based on a comprehensive clinical and morphological research of PTM defined morphological criteria of probable aggressive behavior, favorable prognosis and do not affect the clinical course of the disease. Supplemented scientific data about the features and prognostic value of epithelial-mesenchymal transformation in PTM. It is shown that microfollicular-solid variant of PTM structure which has the most aggressive biological behavior characterized by a high level expression of vimentin and associated with increased expression of MMP-9, VEGF, reduced expression of NIS and TTF-1. The favorable morphological prognostic criteria of PTM are: follicular variant of structure, unifocal growth, lack desmoplasia, the presence of mixed mature and solely mature stroma, and the absence or severe peritumoral infiltration of immunocompetent cells. The Signs of possible aggressive clinical behavior of PTM include microfollicular-solid variant of the structure, the loss of tumor cell polarity and sell connection, extrathyroid extension, multifocal growth, high level of desmoplasia, the presence of extremely immature or young mixed tumor stroma, weak peritumoral infiltration of immunocompetent cells. No correlation was found between sex, age, size of microcarcinomas, concomitant thyroid pathology, tumor localization, papillary or mixed papillary-follicular structure and features such as an aggressive clinical course of metastasis, extrathyroid extension, advanced stage of disease.