"The diagnostic accuracy of thyroid nodule fine-needle aspiration cytology following thyroid surgery: a case-control study".

Thyroid surgery may cause regional scarring and some degree of fibrotic process which may extend into the perithyroidal soft tissues. This may result in problems when collecting thyroid fine-needle aspiration biopsy (FNAB) samples and evaluating the cellular abnormalities. This study aimed to determine if a history of thyroid surgery is a risk factor for nondiagnostic (ND) FNAB results. Patients with ≥1 discrete nodular lesion of the thyroid who underwent FNAB were included. The patients with a history of thyroid surgery constituted group 1, and the others constituted group 2. The factors which may influence FNAB results, including age, gender, presence of Hashimoto's thyroiditis, and ultrasound characteristics, were also evaluated. Group 1 included 123 patients with 200 nodules, and group 2 included 132 patients with 200 nodules. The two groups were similar with respect to demographic characteristics of the patients and ultrasonographic features of the nodules including diameter, content (cystic or solid), echogenicity, margin, and calcifications (P > 0.05). In all, 176 (44 %) of the participants had ND FNAB results. The median time interval between thyroid surgery and FNAB was 15 years [range, 1-45 years; interquartile range (IQR) 13 years]. Significantly more nodules in group 1 had ND FNAB results than in group 2 [98 (49 %) vs 78 (39 %), respectively, P = 0.028]. Multivariate analysis revealed that history of thyroid surgery was independently associated with ND FNAB [odds ratio (OR) 1.55, 95 % confidence interval (CI) 1-2.33, P = 0.033]. A history of thyroid surgery increases the risk of initial ND FNAB.