PMC10028173_01
The 18F-FDG PET/CT imaging before treatment. The MIP picture (A) revealed hypermetabolic foci in the retroperitoneum and mediastinum (arrows). On the axial images, several low-density lesions were detected in the right inguinal region (SUVmax 12.1)(solid arrows) (B: CT, C: PET, D: fusion). The image (E: CT, F: PET, G: fusion) revealed numerous lymph nodes with abnormal metabolic confluence and a SUVmax of 9.8. (dotted arrows). Some retroperitoneal hypermetabolic foci (SUVmax 10.2) were found (thin arrows) (H: CT, I: PET, J: fusion).
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Except for multiple significantly enhanced 18F-FDG activity foci in the pelvic cavity and inguinal area, the maximum intensity projection (MIP) image ( Figure 1A ) revealed abnormal activity in the mediastinum and retroperitoneum (arrows). On the axial images ( Figure 1B : CT,  C : PET,  D : fusion), several hypermetabolic foci were observed in the right inguinal region, which corresponded to heterogeneous low-density enlarged lymph nodes (solid arrows), and the maximum standardized uptake value (SUVmax) of the lesion was 12.1. The abdomen axial imaging ( Figure 1E : CT,  F : PET,  G : fusion) revealed multiple lymph nodes of activity (dotted arrows) along the right common iliac vessels and parts of lesions accompanied by fusion. In the axial pictures, a lymph node with elevated activity (thin arrows) surrounding the descending aorta (SUVmax, 10.2) ( Figure 1H : CT,  I : PET,  J : fusion).
The delay 18F-FDG PET/CT revealed elevated activity foci in the mediastinum, with a SUVmax of 7.0. The CT scan revealed a single, low-density lymph node nearby the aortic arch (arrowheads) (A: PET, B: CT, C: fusion, D: MIP).
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Nevertheless, the axial imaging demonstrated an elevated 18F-FDG lymph node activity around the aortic arch (arrows), with a SUVmax of 7.1. ( Figure 2A : PET,  B : CT,  C : fusion,  D : MIP).
The puncture biopsy specimen pathological findings show infiltration of myofibroblasts, and there is no inflammatory cells (hematoxylin-eosin x200) (A). The immunohistochemistry staining for SMA was positive, indicating a LGMS (B).
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Histopathological examination (hematoxylin-eosin 200) of the specimens obtained from the right inguinal mass revealed spindle-shaped cells arranged in fascicles ( Figure 3 ).
The CT scans following two cycles of treatment. There were still lesions in the mediastinum, retroperitoneum, pelvic, and inguinal regions and the size and quantity of lymph nodes had not decreased significantly from pre-treatment imaging (arrows) (A-D).
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The CT of the chest, abdomen and pelvic cavity indicated no change in the quantity or volume of lesions, and the largest mass measured approximately 8.9cm x 7.1cm ( Figure 4 ).