PMC9853067_01
CT images.
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The chest CT scan revealed a well-defined irregular mass of 17 x 10 x 7.5 cm3 in the right anterior mediastinum, with strip-like low-density shadows in the lesion, and a CT value of approximately -67 Hounsfield units, thereby suggesting adipose tissue ( Figure 1 ). The arterial phase showed less vascularity and heterogeneous hypodensity within the lesion (A, white arrow;  Figure 1 ); the venous phase showed persistent hypodensity (B, white arrow;  Figure 1 ) with compression of the cardiac cavity, right main bronchus, and occlusion of the right main bronchus (C, red arrow;  Figure 1 ) ; the compressed right main bronchus and corresponding lung tissue returned to normal (D, black arrow;  Figure 1 ) one week after the patient underwent chest surgery.
18F FDG PETCT images and pathologic picture.
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CT scan of the chest, 18F-FDG PET/CT was performed owing to concerns that the lesion may be malignant. Coronal PET/CT fusion images (A;  Figure 2 ) show a large, heterogeneous hypermetabolic mass in the right thorax (white arrows;  Figure 2 ), whereas the thyroid was normal and not hypermetabolic (green arrows;  Figure 2 ), thereby suggesting a thymic origin of the mass. PET/CT fusion; D: PET;  Figure 2 ), the uptake of FDG with an SUVmax of 7.1 (white and black arrows;  Figure 2 ) shows that the mass has heterogeneous hyperactivity. Pathological images (E, hematoxylin-eosin stain; original magnification x 100) showed histologically normal thymic tissue consisting of lobules with well-defined cortical and medullary cells.