The Role of [ 18 F]FDG PET/CT in the Characterization of Thymic Epithelial Tumors at Initial Stage.

Purpose: The aim of this study was to evaluate the potential role of [ ¹⁸ F]FDG positron emission tomography/computed tomography (PET/CT) in the characterization of thymic epithelial tumors (TETs). Materials and Methods: A total of 73 patients who underwent preoperative [ ¹⁸ F]FDG PET/CT were included in this study. Visual total score (VTS), maximum standard uptake values (SUV _max ), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and heterogeneity index (HI) parameters were analyzed to investigate the prediction of histopathologic grade and advanced stage. Results: The cohort included 26 patients with low-grade thymoma (LGT), 36 patients with high-grade thymoma (HGT), and 11 patients with thymic carcinoma (TC). Ninety-one percent of TC had VTS >2, whereas 31% of LGT and 75% of HGT had VTS >2. SUV _max , MTV, and TLG were statistically significantly higher in the TC group than in both thymoma and HGT. Using the cutoff value of 7.25 for SUV _max , TC was differentiated from thymomas with 91% sensitivity and 74% specificity. TC had significantly lower HI values than thymomas. HI parameters showed good diagnostic ability to differentiate TC from thymoma and TC from HGT. SUV _max , MTV, and TLG were significantly higher in advanced-stage disease than in early-stage disease. Conclusions: Visual and quantitative parameters can reliably predict both advanced disease and the grade of primary tumor in TETs. Therefore, as a promising metabolic imaging method, [ ¹⁸ F]FDG PET/CT makes important contributions to preoperative evaluation in routine clinical practice.