CURRENT IDEAS ABOUT THE CLINICAL AND BIOLOGICAL FEATURES OF RADIOIODINE-REFRACTORY METASTASES OF PAPILLARY THYROID CANCER, THE MECHANISMS DRIVING THEIR DEVELOPMENT, AND PREDICTION METHODS
The current problem in the diagnosis and treatment of differentiated thyroid cancer is radioiodine-refractory metastases, which occur in 4–20% of cases, the cells of which are unable to accumulate radioiodine, and radioiodine therapy for which becomes ineffective. The loss of the ability to accumulate radioiodine inversely correlates with the survival in thyroid cancer patients; the average median survival is reduced to 2.5–3.5 years in patients with distant radioiodine-refractory metastases. The purpose of this review (supplemented with our own data) was to analyze the literature on the known mechanisms of radioiodine accumulation by thyroid cells and their alterations underlying the development of radioiodine resistance of thyroid cancer, the clinical and biological features of radioiodine-refractory metastases, the methods of cells’ radioiodine concentrating ability restoration and the known ways of radioiodine resistance prognosis. The analysis of scientific literature prompted a pilot comprehensive cytological, cytochemical and immunocytochemical study of fine-needle aspiration smears of radioiodine-refractory metastases (compared with the corresponding groups of papillary carcinomas and their metastases) and revealed the characteristic cytological features of radioiodine-refractory cells (the low content of thyroid peroxidase and thyroglobulin, phenotypic heterogeneity of the epithelium), which allowed to create on their basis methods of preoperative prognosis of radioiodine resistance of thyroid carcinoma.
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