Focal thyroid incidentalomas identified with whole-body FDG-PET warrant further investigation

Fluorodeoxyglucose (FDG) whole body positron emission computed tomography (PET-CT) detects clinically occult malignancy. The aim of this study was to assess the prevalence and significance of focal thyroid 18F - fluorodeoxyglucose uptake. A retrospective review of all patients who had FDG PET-CT examinations, in a single tertiary referral centre was performed. PET scan findings and the final pathological diagnosis were collated. 2105 scans were reviewed. Focal uptake was identified in 35 (1.66%) patients. Final surgical histology was available on eight patients, which confirmed papillary carcinoma in four (20%) patients and lymphoma and metastatic disease in two patients respectively. This gave an overall malignancy rate in focal thyroid uptake of at least 33%. Thyroid incidentalomas occurred with a frequency of 2.13%, with an associated malignancy rate of at least 33% in focal thyroid uptake. The high malignancy rate associated with focal thyroid uptake mandates further investigation in medically fit patients.