The increasing role of PET-CT in oncological and non-oncological conditions has resulted in an increased detection of PET-CT incidentalomas, commonly involving the thyroid gland [1, 2 and 3].
The tracer 18-Fluorodeoxyglucose (18F-FDG) used in PET-CT can incidentally accumulate in the thyroid gland, either diffusely or focally. Incidental focal 18F-FDG uptake within thyroid gland has previously been found to occur in 1.2–4.3% of all PET-CT scans in patients scanned for an alternative indication [4, 5, 6, 7, 8, 9, and 11].
Patients with focal uptake within thyroid gland are at a higher risk of malignancy, with studies reporting between 26% and 50% [4, 5, 6, 8, 9, 12, 13, and 14]. Further investigation of focal 18F-FDG uptake with ultrasound and Fine needle aspiration cytology (FNAC) is recommended because of this increased risk of malignancy [15, 16, and 17].
PET-CT can deduce semi-quantitative evaluations of glucose metabolism in tissues by measuring Standardized Uptake Value (SUVmax) [18]. The role of SUVmax in thyroid malignancy is debated as studies have produced conflicting results and, although reasonable to suggest that malignancy is associated with a higher SUVmax value [19], some studies have shown no correlation [20, 21].
Although the usefulness of SUVmax in thyroid malignancy is questioned, a cytological diagnosis of focal thyroid FDG‐PET incidentalomas is necessary considering the increased risk of malignancy.
The primary aim of our study was to quantify incidental thyroid malignancy on 18F-FDG PET-CT in patients scanned for an alternative indication. A secondary outcome was to compare mean, median and range of SUVmax according to thyroid malignancy subtypes.