Ultrasound-guided fine-needle aspiration biopsy of thyroid nodules: comparison in efficacy according to nodule size.

BACKGROUND: The objective of this study was to compare the efficacy and procedure time of ultrasound-guided fine-needle aspiration biopsy (US-FNAB) of thyroid nodules, according to the nodule size.

METHODS: US-FNABs of thyroid nodules performed between June 2007 and December 2007 were studied. We divided these patients into three groups according to the largest diameter of their nodules. Group A consisted of patients with thyroid nodules less than or equal to 5 mm, group B of patients with thyroid nodules greater than 5 mm and less than or equal to 10 mm, and group C of patients with thyroid nodules greater than 10 mm. We retrospectively reviewed the cytopathology results and complications in all three patient groups and measured the separate, total US-FNAB procedure time for each of 20 randomly selected thyroid nodules.

RESULTS: US-FNAB was performed on 438 thyroid nodules in 253 patients. In groups A, B, and C, the adequacy rates from the first US-FNAB were 79.6% (90/113), 90.6% (125/138), and 95.2% (178/187), respectively. In groups A, B, and C, 113, 138, and 187 thyroid nodules in 100, 120, and 169 patients, respectively, revealed 59, 75, and 126 benign; 12, 11, and 9 suspicious for malignancy; 9, 32, and 29 malignant; 10, 7, and 14 inderminate for malignancy; and 23, 13, and 9 inadequate on the first US-FNAB. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were determined to be 85.7%, 100%, 100%, 94.9%, and 96.1% in group A; 97.7%, 100%, 100%, 98.7%, and 99.1% in group B; and 100%, 99.2%, 97.1%, 100%, and 99.4% in group C. The mean procedure times in groups A, B, and C were 2 minutes 33 seconds, 1 minute 50 seconds, and 1 minute 32 seconds, respectively. There were no significant patient complications in any of the three patient groups.

CONCLUSIONS: US-FNAB of thyroid nodules smaller than 5 mm in maximum diameter was less successful, and the sensitivity was lower than those of nodules larger than 5 mm. We considered, however, that the sampling adequacy and efficacy of US-FNAB of thyroid nodules less than 5 mm in maximum diameter was satisfactory in our series and should be similar in other centers with similar characteristics to ours.