Intraoperative frozen section examination and current changes in the pathological diagnosis of thyroid tumors

The aim — to determine the effectiveness of intraoperative frozen section examination (FSE) of thyroid nodular pathology in patients aged <18 years at the time of the Chernobyl accident in identifying of papillary thyroid carcinoma (PTC), and to determine justified indications for the performance of intraoperative FSE, taking into account changes in the pathological diagnoses of thyroid tumors at the present time. Materials and methods. The analysis of the results of FSE in 406 patients with nodular thyroid lesions operated during the 2009-2014 and 2015-2017 with availability of the cytological conclusions after FNA, has been performed. The results of FSE for each study period were compared with the final pathological diagnoses and the FNA conclusions. Results. A significant increase in the effectiveness of the FSE during 2015-2017 in identifying the PTC in comparison with 2009-2014 was revealed, due to an increase in the percentage of cases referred to the FSE with a cytological conclusion after FNA «suspicion of carcinoma» and a decrease in the percentage of cases with uncertain conclusion after FNA «follicular neoplasm». It has been proved that the FSE effectiveness is almost 100% for non-encapsulated PTC, but in the presence of a complete tumor capsule it decreases to 30-37%. Conclusions. The only FNA conclusion «suspicion of carcinoma» (level V according to TBSRTC) is fully justified for FSE performing, because FSE in such case can significantly influence the choice of adequate surgical intervention. At the FNA conclusions such as «follicular neoplasm», «atypia», «benign lesion» (IV, III and II levels according to TBSRTC), FSE is unreasonable.