Objective: The aim of this study is to analyze the relationship between thyroid nodules detected in patients who were examined in our clinic for any indication and had 18fluoro-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) scanning and thyroid cancer.

Methods: Results of patients who had FDG PET/CT scanning for any indication other than thyroid cancer during 2015 and 2016 in Okmeydani Training and Research Hospital were examined. Age and genders of patients, FDG PET scanning indications, FDG accumulation type (focal
or diffuse), lesion maximum standard uptake value (SUVmax), histology, and pathology of the patient who had fine-needle aspiration biopsy (FNAB) or surgery were recorded. According to the results obtained from these values, the relationship between thyroid nodules and thyroid cancer was analyzed.

Results: Among the group of 50 patients, 18F-FDG PET/CT scanning detected all as having thyroid nodules. Forty cases had benign diagnoses, whereas ten cases had malignant diagnoses either by FNAB or total thyroidectomy. According to the diagnosis results, the SUVmax average of the malignant group was higher than the SUVmax average of the benign group. However, no statistically significant result was obtained (p>0.05). The results also showed no statistically significant association regarding tumor size between the malignant and benign groups (p>0.05).

Conclusion: Thyroid incidentaloma was detected among patients who had 18F-FDG PET/CT scanning for any reason other than thyroid cancer. Thyroid malignancy was detected in 20% of patients diagnosed with thyroid nodules by with focal 18F-FDG accumulation. No statistically significant results concerning SUVmax value and lesion size were obtained among groups having benign and malignant diagnoses. Since no significant results were obtained between the SUVmax and malignancy, no threshold value for SUVmax was calculated.