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General Clinical Specialties: General Practice-OncologyGeneral Practice-Oncology Posters |
1 Nuclear Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania; 2 Nuclear Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
1060
Objectives: Incidental lesions with FDG uptake in the thyroid are increasingly being discovered during FDG-PET. Accurate characterization of these FDG-avid thyroid incidentalomas remains a challenge for nuclear medicine physicians, whereas determination of the most appropriate management presents a dilemma for referring physicians. The study was to characterize the prevalence and risk of malignancy for thyroid incidentalomas found on FDG-PET/CT scan in a relatively large population.
Methods: 2594 cases of FDG-PET/CT performed at our institute in the past 1.5 years were retrospectively reviewed. Scans with incidental thyroid uptake were identified. Data relating to PET findings, thyroid functional assay, and pathological diagnosis were analyzed. Thyroid incidentaloma was defined as a new thyroid lesion initially identified on the PET scan in a patient without a history of thyroid disease.
Results: The prevalence of thyroid incidentalomas was 3.8%(99/2594) on FDG-PET/CT, of which 46.5%(46/99) were diffuse and 53.5%(53/99) were focal. Of the 46 diffuse cases, 21 had thyroid functional assay and/or US. Presumptive diagnosis of thyroiditis was possible in all of the 21 cases. 11 patients with focal uptake had FNA or post surgical pathological data: 5(45.5%)primary thyroid cancers, 4(36.4%) benign lesions, and 2(18.2%) metastasis. Mean SUVmax was higher in malignant compared to benign lesions, but there was overlapping.
Conclusions: Thyroid incidentaloma identified by FDG-PET/CT occurred with a frequency of 3.8%, with about half of focal and half of diffuse uptake. The risk of primary thyroid malignancy was 45.5% in lesions with focal uptake while the majority of diffuse uptake cases represent chronic thyroiditis.
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