EVALUATION OF THYROID-NODULES FOR MALIGNANCY USING TC-99(M)-SESTAMIBI

Tc-99(m)-sestamibi (Tc-99(m)-MIBI) is used for myocardial perfusion imaging but has also been reported to localize in tumours. The usual thyroid scanning radionuclide is Tc-99(m)-pertechnetate. Altogether, 161 patients with clinically solitary thyroid nodules had both Tc-99(m)-MIBI and Tc-99(m)-pertechnetate thyroid scans, with the nodules being reported as cold, warm or hot. Fine-needle aspiration cytology (FNAC) and surgery were performed in those patients who consented to these procedures. Of 131 patients who had FNAC, only 58 proceeded to surgery. In the surgically treated group, 14 of 58 (24%) were confirmed to have thyroid cancer, whereas 44 of 58 (76%) had benign lesions. The 14 cancerous nodules were cold on the Tc-99(m)-pertechnetate scan, whereas with Tc-99(m)-MIBI 11 were warm and 3 were either cold or hot nodules. Of the 44 benign lesions, 18 were cold, 9 were warm and 17 were hot nodules. In those 131 patients who had FNAC, the cytology was reported as benign in 120 of the nodules and malignant in 11. The three false-negative cytologies were reported as follicular adenomas. The benign lesions noted on FNAC and surgery were thyroiditis, adenomas and haemorrhagic or colloid cysts. The results from the 58 surgically treated patients suggest that the warm nodules would need surgery, whereas the cold and hot nodules are unlikely to be malignant. The overall sensitivitiy of the Tc-99(m)-MIBI scan was 79% and the specificity 80%, with the warm nodule on Tc-99(m)-MIBI scan having a positive predictive value of 55% and a negative predictive value of 92%.