Objective: To evaluate the accuracy of fine needle aspiration cytology (FNAC) of thyroid lesions in Ramathibodi patients.
Material and Method: A retrospective review is performed on 469 cases of thyroid surgical pathology specimens with previous FNAC reports; during January 2005 to January 2008. All histopathology reports are compared to the latest previous cytopathology results which are categorized as unsatisfactory, benign, inconclusive, borderline and malignancy.
Results: The cytopathology results showed 74 cases (15.7%) of unsatisfactory specimens, 243 cases (51.8%) of benign lesions, 33 cases (7%) of inconclusive lesions, 15 cases (3.2%) of borderline lesions and 104 cases (22%) of malignant lesions. The histopathology results for benign lesions reveal multinodular and nodular goiter of 236 cases and other diagnosis of 54 cases. The histopathology results for malignant lesions were papillary carcinoma of 147 cases, follicular carcinoma of 24 cases and other malignancy of 8 cases. Among 243 cases of benign from FNAC; 23 cases turn out to be malignancy while 104 cases of malignancy from FNAC show no false positive. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of FNAC are 81.9%, 100%, 100%, 90.4% and 93.4% respectively.
Conclusion: FNAC is a minimally invasive, highly accurate and cost-effective procedure. In our setting the FNAC enable the clinician to “rule-in” malignant lesions with confidence.

Keywords: Accuracy, Fine needle aspiration, Lesion, Thyroid