Usefulness of Tc-99m-pertechnetate scintigraphy and fine-needle aspiration cytology in patients with solitary thyroid nodules and thyroid cancer

The aim of this study was to evaluate the accuracy of fine-needle aspiration (FNA) cytology and thyroid scintigraphy (TS) in patients with solitary thyroid nodules. We retrospectively reviewed a series of 657 consecutive patients (531 (80.8%) women and 126 (19.2%) men, median age 45 years, range 16-81 years) with solitary thyroid nodules. Prior to surgery, all patients underwent FNA cytology whilst 99mTc-pertechnetate TS was performed in 496 (75.5%) patients. Final histopathology showed 533 (81.1%) benign nodules, including 251 (38.2%) follicular adenomas and 124 (18.9%) thyroid carcinomas. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy in the detection of thyroid cancer were 95.8%, 21.1%, 22.6%, 95.5% and 35.7% for TS, and 81.4%, 99.4%, 97.1%, 95.8% and 96.0% for FNA cytology. The presence of thyroid cancer was confirmed in 92 out of 407 (22.6%) patients with a "cold" nodule, in 4 (4.5%) patients who had normal or increased uptake on TS, in 101 out of 104 (97.1%) patients with smears suggesting malignancy, and in 3 out of 533 (0.6%) smears suggesting benign lesions. In conclusion, the specificity of TS is low and this technique should be abandoned as a routine test in patients with nontoxic thyroid nodules. However, a more careful evaluation should be suggested for patients with cold thyroid nodules and a FNA cytology that reads follicular neoplasm.