The radiologic work-up in thyroid surgery: fine-needle biopsy versus scintigraphy and ultrasound

To compare the effectiveness and predictive value of radiologic studies with fine-needle aspiration biopsy (FNAB) in correctly diagnosing thyroid lesions, we reviewed the medical records of 441 patients who had been treated surgically for thyroid disease from 1987 through 1999. We compared the results of thyroid scintigraphy, ultrasound, and FNAB with findings on final surgical pathology. The data were analyzed according to the chi-squared (chi 2) test. Of 189 thyroid scintigraphy scans that showed a hypofunctional (cold) nodule, 52 (27.5%) were found to be cancerous, and of 35 hyperfunctional (hot) nodules, two (5.7%) were malignant (sensitivity = 91%; specificity = 19%; accuracy = 38%; chi 2 = 7.67; p = 0.006). Of 66 ultrasounds that detected a solid or a mixed solid-cystic mass, 16(24.2%) were cancerous, while none of the eight sonograms that showed a purely cystic lesion was malignant (sensitivity = 100%; specificity = 14%; accuracy = 32%; chi 2 = 2.47; p = 0.116 [not statistically significant]). Of the 119 patients whose FNABs were diagnostic, 55 biopsies revealed follicular cells. Of the remaining 64 biopsies, cancer was correctly predicted in 35 of 44 patients (79.5%) and benign disease was correctly diagnosed in 18 of 20 patients (90.0%) (sensitivity = 95%; specificity = 67%; accuracy = 83%; chi 2 = 27.3; p = 0.00). We conclude that in the evaluation of thyroid lesions, FNAB is superior to imaging studies, which yield a relatively high rate of false-positive results.