Unsatisfactory Ultrasound-Guided Fine Needle Aspiration of Thyroid Nodule: Which Factors Limit Cytology Result?

Objective: The purpose of this study is to focus on which factors affect or limit fine-needle aspirationcytology (FNAC) results of thyroid nodule, in order to increase the satisfactory cytologic results and to avoid unnecessary FNAC in patients with asymptomatic benign nodules and highly possible unsatisfactory results. Materials and Methods: The records of 217 thyroid nodules in 179 patients referred to the radiology department at Lerdsin Hospital for US-guided FNAC between January 2010 and December 2013 were retrospectively reviewed. Cytologic specimens of the FNAC were classified as unsatisfactory (non-diagnostic) and satisfactory (diagnostic) results and analyzed by mean of Logistic regression analysis, based on patientûs age, gender, nodule size, number and solid-cystic composition of nodule. Results: The cytologic result was satisfactory for diagnosis in 154 specimens (71%) and unsatisfactory in 63 specimens (29%). Patientûs age, gender, number and size of nodule of the unsatisfactory result group were not different from the satisfactory result group but the nodule composition was different. Percentage of the unsatisfactory aspiration increased as the cystic component increased, ranging from 15.3% in solid nodules to 59.3% in predominant cystic nodules (cystic >75%). Upon the binary logistic regression analysis, the predominant cystic nodule was the only significant predictor of unsatisfactory result (p-value < 0.001) while solid nodules, predominant solid nodules and solid-cystic nodules are not significant. Unsatisfactory FNAC result of the predominant cystic nodules was about 8 times higher than the solid nodule (crude odds ratio = 8.087, p-value < 0.001). Conclusion: To optimize the usefulness of FNAC,we should realize that solid-cystic composition of the thyroid nodules influence the non-diagnostic and diagnostic cytology.