PMC8526269_01
Neck and chest CT. The sagittal image revealed a mediastinal mass (41 x 29 mm) with clear demarcation form the right lobe of the thyroid gland. The coronal image shows the mediastinal mass interposing between the trachea and supra-aortic vessels.
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Imaging by computed tomography (CT) documented a large mediastinal mass (41 x 29 mm) inferior to the right lobe of the thyroid gland, interposing between the trachea and supra-aortic vessels, with probable tracheal and mediastinal vessel infiltration (Figure 1). The mass was initially considered a mediastinal lymph node due to its clear demarcation from the adjacent thyroid gland (Figure 1).
99mPertechnetate scintigraphy showing increased diffuse uptake in the thyroid parenchyma and the absence of uptake in the mediastinal mass.
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Blood tests identified overt hyperthyroidism due to Graves' disease: TSH <0.02 muUI/mL (NR: 0.30-4.20), free thyroxine (FT4) 3.86 ng/dL (NR: 0.90-1.70), free triiodothyronine (FT3) 9.2  pg/mL (NR: 2.0-4.4), and thyroid-stimulating antibodies (TRABS) 21.9 UI/L (NR: <1.8). 99mPertechnetate scintigraphy showed increased diffuse uptake in the thyroid parenchyma but the absence of uptake in the paratracheal mass and in the lung nodules (Figure 2).
FDG-PET revealed multiple lesions with intense FDG uptake due to malignant disease (thyroid, mediastinal lymph nodes, lungs, bone, muscle, heart, liver, and adrenal).
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Restaging fluorodeoxyglucose- (FDG-) positron emission tomography (PET) showed intense uptake in the right lobe of the thyroid gland, lymph nodes, lungs, pleura, bone, muscle, myocardium, liver, kidney, and adrenal gland (Figure 3).