The Reliability of Fine-Needle Aspiration Biopsy in Terms of Malignancy in Patients With Hashimoto Thyroiditis

The aim of this study was to analyze the presence of malignancy in patients with Hashimoto''s thyroiditis and to investigate the reliability of preoperative fine-needle aspiration biopsy (FNAB). The retrospective study included 44 patients who were operated on for nodular goiter between December 2010 and October 2011. The patients underwent thyroidectomy following a cytologic analysis plus FNAB. Hashimoto''s thyroiditis was confirmed on histopathology in all patients. FNAB results were defined as benign in 14 (31.8%), suspicion for malignancy in 17 (38.6%), malignant in 9 (20.5%), and inadequate in 4 (9.1%). Following the thyroidectomy, presence of papillary thyroid carcinoma and follicular variant of papillary thyroid carcinoma were detected in 10 patients (22.7%) and 1 (2.3%) patient, respectively. The FNAB results were interpreted in terms of malignancy, which revealed the sensitivity as 80%; specificity, 40%; false positives, 69.2%; false negatives, 14.3%; positive predictive value, 31.8%; negative predictive value, 85.7%; and diagnostic accuracy, 50%. The coexistence of Hashimoto''s thyroiditis with papillary thyroid carcinoma is quite common. The FNAB results for such cases are hard to evaluate, and they are likely to increase the number of false positives.Key words: Hashimoto''s thyroiditis, Papillary thyroid carcinoma, Fine needle aspiration biopsyHashimoto''s thyroiditis (HT) is also known as chronic lymphocytic thyroiditis, with an incidence rate of 1% to 4% and incidence of 3 to 6 per 10,000 individuals per year.¹ It is the second most common thyroid lesion next to endemic goiter, and it is more frequent in women.² It generally presents as diffuse goiter, while its presentation as 1 or 2 predominant nodules is quite rare. In the preoperative stage, it is quite difficult to determine whether these nodules are caused by HT or by an HT-related malignancy. There are numerous studies suggesting that there is a strong relation between HT and thyroid neoplasms and that HT leads to a higher incidence rate for thyroid malignancy.³ However, Pradeep et al⁴ have reported that they did not observe any associated malignancy in HT in their series.Fine-needle aspiration biopsy (FNAB) is a safe procedure, which is well defined for the primary diagnosis of thyroid patients.⁵ The initial aim in performing FNAB is to identify the thyroid nodules that require surgery and decrease the overall incidences of thyroidectomy in patients with benign diseases.^6,7 FNAB is reported as a superior and cost-effective procedure for the diagnosis of HT, as compared with antibody testing.⁸ Nevertheless, the false positives and false negatives in FNAB lead to a diagnostic pitfall.⁶The aim of this study was to analyze the presence of malignancy in HT patients and to investigate the reliability of FNAB through a comparison between pre- and postoperative histopathologic results.