Incidental Thyroid Lesions Detected with FDG PET Scanning

Abstract

Aims: fluorodeoxyglucose Positron EmissionTomography(FDG PET) scanning has become more popular in recent years, it has also become more frequent means of detecting incidental thyroid lesions. The aim of this study is to investigate to prevalence of incidentally found thyroid lesions in patients undergoing FDG PET and determine the risk for thyroid cancer. FDG PET was performed on 5758 patients for evaluation of suspected or known cancer without any history of thyroid disease between January 2006 and May 2012 in our clinic. Material and methods: Patients with incidental thyroid abnormalities were identified. Medical records related to the FDG PET findings including standardized uptake value(SUV) and pattern of FDG uptake, fine needle aspiration(FNA) diagnosis and histopathology after thyroid surgery were reviewed retrospectively. Results: One hundred twenty three patients (2.1%) were identified to have focal incidental thyroid lesions and 52 patients (0.9%) were identified diffuse incidental thyroid lesions on FDG PET. Twenty-four patients with focal and 5 patients with diffuse incidental thyroid lesion underwent FNA. The malignant diagnosis was detected in 41.6% of focal lesions. In diffuse lesions, malignant diagnosis was not observed. There was a significant difference in the SUVmax between the benign and malignant lesions (5.7 +/- 2.2 and 10.1 +/- 5 3). Malignant diagnosis was noted in 57.1% of male patients and 20% of female patients who underwent FNA. Conclusion: The results of this study suggest that focal FDG uptake, high SUV and male gender have high risks for thyroid malignancy in incidentally found thyroid lesions by FDG PET. Further diagnostic work-up is needed in patients with these findings.