Objectives. To determine the prevalence of incidentalomas in a patient population with no known thyroid malignancy who underwent whole body FDG-PET/CT for staging or restaging of neoplasia. The additional aim of the study was to evaluate the feasibility of using PETCT as a screening tool for malignant thyroid incidentalomas. Methods. Retrospective review of medical records of all the thyroid exams done at our institution between January 1, 2000 and August 20, 2008. We made a criterion of PET/CT as the primary method of detection of incidentalomas. Results. From a total of 8464 thyroid exams, 156 incidentalomas were found and 40 incidentalomas underwent anatomopathology analysis, which was used as gold standard. Chi-square analysis was used to analyze the data. There is no significant association between SUV value and the prevalence of incidentalomas. Discussion. From January 1, 2000 to August 20, 2008, incidentalomas have a prevalence of 1.84% at our institution. 38% of the incidentalomas that were biopsied were characterized as representing malignant tumors. Conclusion. Focal, abnormal FDG uptake representing incidentalomas must be followed up with biopsies. It is impractical to use PET/CT as a screening tool to detect incidentalomas for the general population but it must be done in patients with history of any type of cancer. 1. Introduction Thyroid incidentalomas are newly detected thyroid nodules, discovered during a computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US), or positron emission tomography (PET) exam for nonthyroid diseases. They are divided into focal and diffuse types. Focal type is defined as an area of uptake of 2-fluorodeoxyglucose (FDG) in less than one lobe, whereas diffuse type is FDG uptake in the entire thyroid gland. There are guidelines for managing palpable thyroid nodules but there are no such guidelines for nonpalpable nodules [1]. FDG-PET has a reported sensitivity of 75–90% and a specificity of 90% for detecting thyroid malignancies [2]. Whole body FDG-PET/CT combines the technology of whole body CT scan with FDG uptake localization to assess glucose utilization rates. The vast majority of solid tumors have an enhanced glycolytic rate, and they are therefore amenable of being imaged with FDG-PET. FDG-PET has become the standard of practice for staging, restaging, and assessment of therapy response in a variety of malignant solid tumors. Normal thyroid gland shows very low FDG uptake, and some data suggest that a moderate diffuse uptake can represent a normal variant [3]. However, FDG has high
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