BACKGROUND/AIM:Positron emission tomography/computed tomography with 18F-fluorodeoxyglucose (18F-FDG PET/CT) is frequently used to differentiate schwannomas from malignant peripheral nerve sheath tumors. Schwannomas exhibit pathological heterogeneity, with highly cellular (Antoni A) and hypocellular (Antoni B) areas, but current PET/CT methods do not adequately reflect this heterogeneity. This study aimed to compare imaging characteristics of schwannomas in the trunk versus the extremities, with emphasis on metabolic heterogeneity. PATIENTS AND METHODS:This retrospective study included patients with solitary schwannomas who underwent MRI and 18F-FDG PET/CT before surgical excision (June 2013-September 2023). Exclusion criteria were plexiform, multiple, biopsy-only lesions, and tumors originating from internal organs. Tumors were classified as trunk or extremity lesions. MRI was used to determine size and volume, while PET/CT measured SUVmax, SUVmean, metabolic tumor volume (MTV), and total lesion glycolysis (TLG). Heterogeneity was assessed using three indices: MTV-to-volume ratio (MTV/volume), SUV-based heterogeneity index (HISUV), and metabolic region-adjusted SUV-based heterogeneity index (MRA-HISUV). RESULTS:Fifty-six patients were included. Trunk schwannomas were larger than extremity tumors in diameter (4.33 cm vs. 2.77 cm; p<0.05) and volume (27.71 cm3 vs. 6.25 cm3; p<0.05). SUVmax (4.09 vs. 3.71) and SUVmean (2.47 vs. 2.22) did not differ significantly. MTV (18.43 cm3 vs. 6.19 cm3, p<0.05) and TLG (58.41 vs. 14.40, p<0.05) were higher in trunk tumors. MTV/volume ratio was lower (0.77 vs. 1.12, p<0.05), while HISUV and MRA-HISUV were higher in trunk schwannomas (1.79 vs. 1.65 and 2.36 vs. 1.49, p<0.05). CONCLUSION:Trunk schwannomas were larger and exhibited higher metabolic activity and heterogeneity. Novel parameters such as MTV/volume and MRA-HISUV may enhance the characterization of schwannoma heterogeneity.
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