Synchronous thyroid cancer on the edge: Incidentalomas of 18F-FDG PET/CT in clinical practice.

Aims: The objective of this study was to discuss the outcomes of the oncology patients whose PET/CT scans show incidental focal thyroid 18F-FDG uptake.

Methods: This retrospective analysis examined 2575 18F-FDG PET/CT scans from 1803 patients with no known thyroid cancer history. The survival rates were analyzed for patients with and without cytopathological evaluation.

Results: Increased metabolic activity of the thyroid was detected in 96 patients. Of those, 72 were diagnosed with a focal uptake of 18F-FDG and 24 subjects had a diffuse uptake. All 72 patients with a focal uptake were referred for ultrasound (US) and fine-needle aspiration cytology (FNAC). Of those patients, 44 were admitted for US and 16 underwent FNAC. The mean SUVmax was 16.0 ± 7.97 for patients with malignant lesions and 3.24 ± 0.88 for patients with benign lesions (p = 0.023). The mortality rate was higher in the patients who were not evaluated with FNAC.

Conclusion: Patients with incidental focally increased thyroid 18F-FDG accumulation on PET/CT are known to have a high risk of malignancy. These patients require additional diagnostic procedures to distinguish the underlying pathology. However, the clinical condition of these patients will be the primary concern when performing these procedures.