Liquid-based cytology improves preoperative diagnostic accuracy of the tall cell variant of papillary thyroid carcinoma.

The tall cell variant (TCV) of papillary thyroid carcinoma (PTC) is the most common among the aggressive variants of the disease. We aimed to investigate the clinicopathologic characteristics of TCV, and evaluate the diagnostic efficacy of liquid-based cytology (LBC) in TCV detection compared with conventional smear in thyroid fine needle aspiration (FNA). A total of 266 consecutive patients (220 women and 46 men) with PTC were enrolled. We analyzed tumor characteristics according to histologic growth patterns as classic, classic PTC with tall cell features, and TCV. The cytomorphologic features of these subtypes were investigated according to the preparation methods of conventional smear and LBC. TCV and classic PTC with tall cell features comprised 4.9% and 6.0% of all tumors, respectively, and were significantly associated with older age at presentation, larger tumor size, high frequency of extrathyroid extension, and BRAF mutation in comparison with classic PTC. However, there was no statistically significant difference in clinicopathologic features between TCV and classic PTC with tall cell features. Tall cells were more easily detected by LBC than by conventional smear. The percentage of tall cells identified using LBC was well correlated with three histologic subtypes. Our results demonstrate that TCV is more common than previously recognized in Korea and any PTC containing tall cells may have identical biological behavior regardless of the precise proportions of tall cells. It is possible to make a preoperative diagnosis of TCV using LBC.