Hürthle cell presence alters the distribution and outcome of categories in the Bethesda system for reporting thyroid cytopathology.

Objectives: We aimed to determine whether the presence of Hürthle cells altered the distribution of categories in the Bethesda system for reporting thyroid cytopathology, or the expected neoplastic and malignant outcome.
Methods: Fine needle aspiration (FNA) cytology reports of Hürthle cells in a 2-year period were evaluated. The distribution of Bethesda system categories and the outcome at partial or complete thyroidectomy were compared for FNAs with and without Hürthle cells.
Results: Of 895 adequate FNAs with Hürthle cells, 764 (85.4%) were classified as benign, 86 (9.6%) as atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), 32 (3.6%) as follicular neoplasm/suspicious for follicular neoplasm (FN/SFN), 12 (1.3%) as suspicious for malignancy (SFM) and one (0.1%) as malignant. Of 10 359 adequate FNAs without Hürthle cells, 9707 (93.7%) were classified as benign, 412 (4.0%) as AUS/FLUS, 77 (0.7%) as FN/SFN, 93 (0.9%) as SFM and 70 (0.7%) as malignant. The distribution of categories in FNAs with and without Hürthle cells was significantly different (P < 0.001) as a result of a decrease in benign and an increase in AUS/FLUS and FN/SFN categories. Among 128 patients with and 582 without Hürthle cells undergoing surgery, the overall neoplastic and malignancy rates were higher in the former than in the latter group (27.3% versus 14.9%, P < 0.001; 21.1% versus 11.7%, P = 0.003; respectively). Although neoplastic and malignant rates were higher in the group with than without Hürthle cells in all categories, the differences were only significant for a neoplastic outcome of benign cytology (15.1% versus 6.0%, P = 0.0013) and a malignant outcome of FN/SFN cytology (63.6% versus 21.9%, P = 0.0108).
Conclusions: We found that the rates of AUS/FLUS and FN/SFN categories in the Bethesda system were higher when Hürthle cells were present. After surgery, neoplastic and malignant outcomes were significantly higher in the Hürthle cell group.
(© 2013 John Wiley & Sons Ltd.)