Zelinska G.V.

Objective: the study of the correlation between the development of radioiodine resistance and the presence of signs of aggressiveness of primary papillary thyroid carcinomas (PC) (invasion of the capsule and vessels, intrathyroid and extrathyroid distribution, presence of metastases and thyroiditis), as well as the presence in the punctates of PC of special subpopulation of thyrocytes. Object and methods: to analyze the aggressiveness characteristics of papillary thyroid carcinomas, histological findings of 109 patients with histological diagnosis «papillary carcinoma» were used. Of these, 67 patients had no signs of recurrence and metastasis on the background of thyroidectomy and radioiodine therapy within 5 years of observation; 42 patients with the development of radioiodine-resistant metastases (RIRM) in the postoperative period. Cytomorphological and imunocytochemical studies were perfomed on the material of Fine Needle Aspiration (FNA) biopsy of 42 RIRM and 44 papillary thyroid carcinomas. Statistical analysis was performed with nonparametric criterion χ2. Results: there was no statistically significant difference between the groups of patients with the appearance of RIRM and no signs of metastasis in the postoperative period with the presence of invasive growth of PC into the tumor capsule, into the the thyroid gland and into the vessel. At the time of PC histologic diagnosis, extrathyroidal spread of carcinoma and regional metastases were more commonly found in the group of patients with RIRM; less frequently observed signs of thyroiditis compared to the group of patients without signs of metastasis. A special subpopulation of cells with impaired expression of epithelial cell adhesion molecules and lack of thyroglobulin expression was detected in the punctates of RIRM and PC. The correlation between the presence of such cells in primary PCs and the incidence of metastases in the postoperative period is shown. Conclusions: the presence of extrathyroid invasion, regional metastases, and the absence of signs of thyroiditis in the material of the primary thyroid PC can be considered as unfavorable histological factors associated with the development of radioiodine resistance. Primary PCs that are the source of RIRM have more aggressive potential than non-metastatic tumors. The presence in cells of primary thyroid PCs of cells of a special subpopulation of thyrocytes demonstrates their participation in metastatic processes and needs further investigation.

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