Usefulness and limitations of fine needle aspiration biopsy of the thyroid gland

Fine needle aspirations biopsy of the thyroid (FNAB) has become an accepted procedure for evaluation of the thyroid nodule, with 899 performed at the Labey Clinic from 1981 to 1990. We examined them by medical record, pathology, and cytology review, with follow-up by chart or personal communication. Three-hundred-forty-five came to surgery, of which 188 (34%) were malignant; the specificity of the aspirate was 97%, sensitivity 92%, with false negative of 8% and false positive of 3%. By comparison, the frozen section had a false negative rate of 1% and false positive rate of 5%. In combination with frozen section, the fine needle aspirate result improved the accuracy of the intraoperative estimate of malignancy (p=0.03). When the aspiration was benign but the lesion was clinicaly suspicious, a cancer was found at surgery in 13% of cases. Of the patients observed for a minimum of 5 years, 1.3% developed a carcinoma. Both cases had a non diagnostic FNAB None of the patients with a clinical and cytological benign lesion developed cancer. The complication rate of FNAB was 1.3% FNAB is a helpful and low risk diagnostic procedure but it needs to be done and read appropriately and its result used within the clinical context. Each medical team needs to monitor their results (continued quality control).