ABSTRACT
PURPOSE: To compare characteristic findings of 18F-FDG PET/CT with ultrasonography of malignant thyroid incidentaloma. MATERIALS AND METHODS: This study enrolled 74 patients receiving ultrasonography after thyroid incidentaloma detected on 18F-FDG PET/CT. We analyzed the size, attenuation, margin, cervical lymphadenopathy, and P-SUV of thyroid incidentaloma in 18F-FDG PET/CT and analyzed the size, internal contents, appearance, border, echo, and calcification patterns of thyroid incidentaloma in ultrasonography. Based on pathologic findings, we investigated findings of 18F-FDG PET/CT and ultrasonography for malignant thyroid incidentaloma. RESULTS: In 18F-FDG PET/CT findings, an ill-defined margin accompanied by cervical lymphadenopathy was more common in malignant (59.1%) than benign (13.2%) lesions (p < 0.05). There were no significant differences in p-SUV between malignant and benign thyroid incidentalomas (4.8+/-18.3 vs. 4.4+/-2.2). In ultrasonographic findings, being taller than wide (1.9% vs. 36.4%), having a well-defined speculated margin (75.5% vs. 22.7%), having marked hypoechoic images (18.9% vs. 31.8%), and having micro (5.7% vs. 22.7%) or macrocalcifications (3.8% vs. 27.3%) were more common in malignant thyroid incidentalomas (p < 0.05). CONCLUSION: Malignant thyroid incidentalomas in 18F-FDG PET/CT have ill-defined margins, and those in ultrasonography were the taller than wide, well defined spiculated margin, and showed micro or macrocalcification.