The dependence of the tumor cells differentiation upon the tumor histoarchitectonics, tumor type and patients' sex is studied immunohistochemically and by the in situ hybridization in 57 cases of thyroid carcinoma in children from the Belarus republic. A significant decrease of thyroglobulin synthesis and accumulation in the solid structures of papillary carcinoma is found. A decrease of the degree of the tumor biological differentiation in males is observed regardless of tumor histoarchitectonics. Increased accumulation of thyroglobulin (without change in its synthesis) in normal follicular epithelium found in parallel with increased intrathyroidal carcinoma dissemination and the size of the dominant tumor needs further investigation.