Cell block is a valuable adjunct to conventional smear for thyroid fine needle aspiration: 2395 cases with histological correlation.
AIMS: Conventional smears (CS) of samples obtained by fine needle aspiration (FNA) have proven useful in thyroid nodules evaluation, but the additional contribution of cell block (CB) has only been investigated in a limited fashion. In this study, we aimed to evaluate whether the auxiliary application of CB adds to the diagnostic accuracy of the CS by a College of American Pathologists-accredited hospital laboratory. METHODS: All thyroid FNA samples processed with CS only or combined CB and CS in West China Hospital from January 2011 to December 2015 were retrospectively collected. All specimens were classified according to Bethesda System, and the distribution of Bethesda (2009) categories was compared between CS and combined CS and CB. Further, we compared the diagnostic performance between these two groups for nodules with follow-up histopathology. RESULTS: A total of 11 011 thyroid nodules from 10 206 patients were included. Of these, 2395 nodules from 2211 patients underwent surgical resection. The unsatisfactory rate decreased significantly from 18.1% to 9.8% in the total group and from 1.7% to 0.8% in the group with surgery after combined use of CS and CB. The proportion of atypia/follicular lesion of undetermined significance also declined slightly. Furthermore, all of the sensitivities, specificities, accuracies and positive predictive values increased significantly after the combined use of CS and CB for different calculation methods. CONCLUSIONS: Combined use of CS and CB can significantly decrease the unsatisfactory rate of thyroid FNAs, improve the diagnostic efficacy, and thus should be routinely applied in thyroid nodule evaluation if available.