DESCRIPTIVE ANALYSIS AND MALIGNANCY RATE OF THYROID INCIDENTALOMA DETECTED BY FDG-PET/CT IN ONCOLOGY PATIENTS

Background and aim: Thyroid incidentaloma has increased consequently with increasing frequency of utilization of the radiological imaging methods in clinical applications. According to common belief, these nodules are mostly benign, and it is not cost-effective to investigate these lesions because it causes excessive cost and labor losses. We aimed to investigate the frequency of thyroid incidentaloma and the malignancy rate in FDG-PET/CT imaging among oncology patients. Materials and methods: A total of 21,000 imaging results of 12,952 oncology patients who underwent FDG-PET/CT for various malignancies between January 2011-September 2020 were scanned. 184 of them with thyroid nodules at the FDG-PET/CT and with no prior thyroid nodule in the USG were selected for the study. Demographic features, thyroid lesion size, maximum standardized uptake (SUVmax) values, thyroid function tests, and histopathological were examined and recorded. Results: The mean age of 184 patients (127-female, 57-male) was 63.7 +/- 12.5 years. Only 45 of these 184 patients had Fine-Needle Aspiration Biopsy (FNAB). Of these 45 patients, 27 patients (60%) had benign histopathology, 9 patients (20%) had the atypia of undetermined significance, and 9 patients (20%) had malignant histopathology. The mean SUVmax values were 6.5 +/- 2.8 and 5.5 +/- 3.2 in the malign group and the benign group respectively. No significant difference was detected between benign and malignant groups in terms of TSH (p= 0.684) and SUVmax value (p= 0.265), but nodule size and patient age were higher in the benign group (p= 0.048 and p= 0.041, respectively). Conclusions: Although clinicians do not perform FNAP in most cases with thyroid incidentaloma detected by FDG-PET/CT in oncology patients, there is a high possibility of a malignant lesion in incidentalomas with these patients. Regardless of SUVmax value and nodule size, thyroid lesions, especially focal involvement detected in FDG-PET/CT imaging should be evaluated by FNAB in this patient group.