Abstract
Purpose: Accurate fine-needle aspiration cytology (FNAC) of thyroid nodules provides the best guidance for thyroid surgery. We assessed the utility of FNAC in the diagnosis of thyroid nodules. Retrospective analysis.
Material and Method: We analyzed records of all patients who underwent FNAC and thyroid surgeries between July 2006 and June 2010 at King Khalid Hospital, King Saud University, Riyadh, Saudi Arabia. Each diagnosis derived from FNAC of thyroid nodule reported by the Bethesda system was matched with the final histopathology result. Specificity, sensitivity, positive and negative predictive value, and diagnostic accuracy were assessed.
Results: Of 275 FNAC, 179 (65.1%) had benign results, 60 (21.8%) atypia of undetermined significance or follicular lesion of undetermined significance, 15 (5.4%) follicular neoplasm or suspicion of follicular neoplasm, 15 (5.4%) were consistent with papillary thyroid carcinoma (PTC), and 6 (2.2%) were suspicious for PTC. Histopathology revealed 204 (74.2%) benign thyroid nodules, 44 (16.0%) PTCs, 18 (6.5%) incidental micro-PTCs in nontarget nodules, 7 (2.5%) follicular thyroid carcinomas, 1 (0.4%) medullary thyroid carcinoma, and 1 (0.4%) Hurthle cell carcinoma. Analysis of 190 cases with FNAC and histopathology results revealed a sensitivity of 66.7%, specificity of 99.4%, positive predictive value of 95.2%, negative predictive value of 94.1%, and diagnostic accuracy of 94.2%. Of 10 cases with false negative results, 9 (90%) were larger than 3.8 cm.
Discussion: FNAC is a highly sensitive and specific method for assessing thyroid nodules. We found a high percentage of atypia or follicular lesions of undetermined significance; this needs to be limited to increase accuracy. We suggest surgery for nodules larger than 3.8 cm regardless of FNAC results due to the high false-negative rate, most likely due to sampling errors.