Evaluation of the Role of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in the Differential Diagnosis of Pleural Lesions

Objective: To retrospectively evaluate the diagnostic performance of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in differentiating benign versus malignant pleural thickening/effusion in patients without a known malignancy, to determine the optimal cutoff for maximum standardized uptake value (SUVmax), and to assess the added value of clinical–radiologic variables for diagnostic accuracy.Methods: Seventy-eight patients who underwent 18F-FDG PET/CT for pleural thickening between January 2018 and October 2023 and had no diagnosis of malignancy were included. SUVmax values of pleural thickening and effusion, thickening pattern, asbestos exposure, and smoking history were analyzed retrospectively.Results: For distinguishing benign from malignant pleural thickening based on SUVmax, sensitivity was 77.27% and specificity was 73.53%, which was statistically significant (p < 0.05). Among 63 patients with pleural effusion, the sensitivity and specificity of an SUVmax-based distinction were 68.8% and 55.3%, respectively, and were not statistically significant (p > 0.05). The optimal SUVmax cutoff was 3.58 for pleural thickening and 1.62 for effusion. FDG uptake was higher in diffuse thickening than in focal thickening (diffuse mean SUVmax 6.38 ± 4.85; focal mean SUVmax 3.95 ± 3.55). Asbestos exposure was significant only in the malignant mesothelioma group (p < 0.05). There was no significant association between malignancy and thickening pattern or smoking history (p > 0.05).Conclusion: 18F-FDG PET/CT is valuable for the differential diagnosis of malignancy in patients with pleural thickening and/or effusion. An SUVmax cutoff of 3.58 provides diagnostic contribution for pleural thickening, whereas evaluation of effusion shows limitations. External validation in larger cohorts is required.