Histopathological changes in thyroid tissue after fine needle aspiration biopsy.

Fine needle aspiration biopsy (FNAB) is a method that is frequently used in the diagnosis for neoplastic and non-neoplastic thyroid lesions. However, despite the contribution of this method to diagnosis, varying degrees of histopathological alterations in thyroid tissue occur due to the trauma caused by the aspiration needle. In this study, we compared the histopathology of the thyroidectomy specimens obtained by FNAB with the specimens obtained without the use of FNAB. A hundred and fifty thyroidectomy specimens obtained by FNAB were compared histopathologically with 150 thyroidectomy specimens (control group) obtained without a FNAB procedure. The thyroidectomy specimens were evaluated for hemorrhage, fibrosis, siderophagia, vascular thrombosis, vascular proliferation, infarction, granulation tissue, cystic degeneration, papillary hyperplasia, nuclear atypia, mitosis, calcification, vascular invasion, capsular distortion (pseudoinvasion), cholesterol clefts, and the presence of metaplasia. The thyroidectomy specimens obtained by FNAB had rates of hemorrhage, siderophagia, granulation tissue, papillary hyperplasia, fibrosis, calcification, capsular distortion, cholesterol clefts (P<0.001), and vascular thrombosis (P=0.001) that were statistically significantly higher than those obtained without FNAB. However, there were no clinically significant differences between the two groups in terms of vascular proliferation, nuclear atypia, mitosis, infarction, and oncocytic and squamous metaplasia. Alterations in thyroid tissue in association with FNAB show a considerable variation. Some of the alterations make diagnosis difficult, even leading to misdiagnosis in favor of carcinoma. Therefore, a thorough knowledge of possible alterations is essential to the differential diagnosis.