PMC9114730_01
MRI examination; (A) Axial T1WI shows hypointense signal of left groin mass (white arrow) and right inguinal lymph nodes (black arrow). (B) Axial T2WI imaging demonstrates slightly high signal intensity in the left groin area (white arrow) and low signal intensity in the right inguinal lymph nodes (black arrow). (C) Contrast-enhanced T1WI with fat suppression: the left groin mass showed uneven enhancement (white arrow), while the right inguinal lymph nodes showed marginal enhancement (black arrow). (D) Sagittal contrast-enhanced T1WI clearly shows the "tail fascial sign" (black arrow). T1WI, T1-weighted images; T2WI, T2-weighted images.
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CT revealed a mass of approximately 3.5 cm x 2.0 cm (vertical diameter x horizontal diameter) in her left vulva, and multiple enlarged lymph nodes were seen in the left groin area ( Supplementary Figure S1 ). Figure 1 . Fluoro18-labeled deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) showed a high FDG concentration in the left groin mass, with a maximum standard uptake value (SUVmax) of 31.38, and increased FDG uptake in the right nodule, with an SUVmax of 28, as shown in  Figure 2 .
PET/CT examination. (A) Whole-body MIP images showed a lumpy hypermetabolic lesion in the left groin (white arrow) and increased nodular uptake of FDG in the right groin (black arrow). (B) Axial CT shows an uneven low-density mass in the left groin (white arrow) and a rounded soft tissue density nodule in the right inguinal region (black arrow). (C) PET and (D) PET/CT fusion images show a hypermetabolic mass in the left groin area with SUVmax of 31.38 (white arrow) and nodules in the right groin area with radioactive uptake with SUVmax of 28.0 (black arrow). MIP, maximum intensity projection; FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography; SUVmax, maximum standard uptake.
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Figure 1 . Fluoro18-labeled deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) showed a high FDG concentration in the left groin mass, with a maximum standard uptake value (SUVmax) of 31.38, and increased FDG uptake in the right nodule, with an SUVmax of 28, as shown in  Figure 2 .
Histopathological findings (HE staining: A, x40; B, x200) show fusiform tumor cells, curving vessels, and myxoid alterations in the stroma. Immunohistochemical staining showing vimentin (C), SMA (D), and CD68 (E) positivity. (F) Histopathological view of the right inguinal lymphadenopathy. HE staining shows irregular squamous cells and horn strains (arrows). HE, hematoxylin and eosin.
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Immunohistochemistry showed positive expression of vimentin, CD68, and partial smooth muscle actin (SMA) and negative expression of beta-catenin, CD, Cluster of differentiation (CD34), desmin, S100, and Signal transducer and activator of transcription (STAT6) in left groin tumor cells, as shown in  Figure 3 .