Background: Studies indicate that incidentally discovered thyroid nodules >or=1 cm in size may have a higher rate of malignancy (7% to 29%) than traditionally discovered nodules (5%). We sought to determine the rate of malignancy in incidental thyroid nodules in patients with other malignancies, and examine the accuracy of ultrasound (US) versus computed tomography (CT) in determining nodule size.
Methods: We evaluated 41 patients with history of another known malignancy (gastrointestinal, 23; breast, 11; other, 7) referred with an incidental thyroid nodule. Patients underwent office-based US and biopsy of nodules >or=1 cm. Surgical intervention was based on biopsy results. We compared nodule size at pathology with size seen on CT or US.
Results: Thirty-five patients met criteria for biopsy. Of the 35, 20 (57%) had atypical biopsy results warranting resection. Sixteen of those 20 underwent surgery. Pathology yielded 4 papillary thyroid cancers (PTC), 4 microPTC, 2 metastatic cancers, and 7 benign lesions. Ultrasound measurement of nodules compared to size measured at pathology had an r2 correlation value of 0.90 with P value <.0001. CT scan had an r2 value of 0.83 and P value of .005.
Conclusions: Incidental thyroid nodules in patients with another primary malignancy warranted resection in 57%. The rate of malignancy in incidental thyroid nodules was 24%, which is above the expected rate of 5% seen in traditionally discovered nodules. US correlation with nodule size at pathology was excellent and superior to CT scan. Incidentally discovered thyroid nodules >or=1 cm, seen in patients with another malignancy, warrant further evaluation.