Risk of Malignancy in FDG-Avid Thyroid Incidentalomas on PET/CT: A Prospective Study

Background Due to a substantial risk of malignancy, patients with focal FDG-avid thyroid incidentalomas (FFTIs) on PET/CT are in most of Denmark referred to Head and Neck Cancer (HNC) fast track programs. The aim of this study was to determine the risk of malignancy in FFTI managed in a HNC fast track program. Methods A prospective cohort study including all patients with FFTI referred to the HNC fast track program, Odense University Hospital between September 1, 2016 and August 31, 2017. Ultrasonography (US) and fine-needle aspiration biopsy (FNAB) were intended to be done in all patients. Nodules with cytology of Bethesda 1, 3, 4, 5, or 6 were planned for surgical removal . Results A total of 104 patients were included. All patients had US and 101 patients (97%) had FNAB. Forty-two patients had benign cytology classified as Bethesda 2. The remaining 62 patients underwent surgery except from 11 patients, mainly due to comorbidity. The overall risk of malignancy for patients with FFTI referred to our HNC fast track program was calculated to be 24% (23/95) based on patients with unequivocal cytology and/or histology. The only statistically significant US characteristic to predict malignancy was the appearance of irregular margins with a sensitivity of 47% and specificity of 96%. Conclusion The risk of malignancy of FFTIs handled in our HNC fast track program is 24%.