Predictive Role of Positron Emission Tomography for Malignancy in Thyroid Nodules Diagnosed as Follicular Neoplasm on Fine-Needle Aspiration Biopsy

Aim: Thyroid nodules with cytology reported as follicular neoplasm represent a diagnostic challenge, as fine-needle aspiration biopsy alone cannot reliably distinguish benign from malignant disease. Although 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) has been proposed as a complementary noninvasive tool, its predictive value in this setting remains controversial. This study aimed to evaluate the predictive role of PET/CT-derived standardized uptake values in differentiating benign and malignant pathology in thyroid nodules diagnosed as follicular neoplasm.Materials and Methods: This prospective observational study included patients diagnosed with follicular neoplasm on fine-needle aspiration biopsy who underwent preoperative FDG PET/CT and subsequent thyroid surgery between November 2019 and November 2020. Maximum standardized uptake values (SUVmax) of thyroid nodules were recorded and compared with final histopathological findings. Diagnostic performance parameters, including sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy, were calculated using fourfold contingency tables.Results: A total of 40 patients were included in the study. Final histopathology revealed malignant disease in 25 patients and benign pathology in 15 patients. Mean SUVmax values did not differ significantly between benign and malignant nodules. Using an SUVmax cutoff value of 2, the distribution of FDG uptake was similar in both groups. FDG PET/CT demonstrated a sensitivity of 60%, a specificity of 47%, a positive predictive value of 65%, a negative predictive value of 41%, and an overall diagnostic accuracy of 55%. No statistically significant association was found between SUVmax values and malignancy..Conclusions: FDG PET/CT may have limited diagnostic performance in distinguishing benign from malignant thyroid nodules diagnosed as follicular neoplasm. SUVmax alone may not provide sufficient discriminatory value for malignancy prediction and may therefore be unsuitable as a standalone criterion in preoperative decision-making.