PMC8299103_01
(A) Ultrasound showed a well-defined heterogeneous hypoechoic mass on the left lower abdomen, (B) the mass close contact with the bladder wall (arrow); (C) Contrast-enhanced ultrasonography (CEUS) presented irregular necrotic areas, heterogeneous enhancement in the arterial phase with quick wash-out (54 s); (D-F) Abdominal CT showed a hypodense solid lesion in the wall of an ileal loop, with areas of necrosis within (arrow).
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Abdominal CT revealed a large, irregular mass in the pelvic cavity ( Figures 1D-F ) that was considered as a intestine diverticulum with an abscess. Ultrasonography revealed a 6.1 3.8 x 4.2 cm irregular, heterogeneous hypoechoic mass in the left lower abdomen ( Figures 1A, B  ). Heterogeneous enhancement, and wash-out time of 54 s on CEUS ( Figure 1C ).
(A-E) PET-CT showed a heterogeneously hypermetabolic pelvic mass, and multiple hypermetabolic nodules were observed in the mesentery; (F) An MRI 2 months after surgery showed an irregular lesion on the right side of the frontal bone, which grew across the skull and invaded the brain tissue.
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The PET-CT was performed revealing a highly metabolic mass in the lower abdomen and multiple metabolic nodules in the mesentery ( Figures 2A-E ). An MRI was performed revealing a 2.3 x 2.1 x 2.3 cm lesion on the right side of the frontal bone ( Figure 2F ).
(A) Gross pathology revealed an ileum tumor specimen with brittle texture and multiple ulcerations on the surface; (B) H&E staining revealed small round blue cells; x40. (C-E) Immunohistochemistry showed positive Ki67, CD99 and Fli-1 staining; x40. (F) Molecular analysis revealed positive EWSR1 fusion genes.
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Gross pathology showed the tumor to be friable and having multiple ulcerations on the surface ( Figure 3A ). H&E sections revealed a small, blue, round tumor ( Figure 3B ). Histopathological examination showed positive CD99, CK (pan), Ki67 (70%+), Fil-1, and CD34 levels ( Figures 3C-E ). Molecular analysis revealed positive EWSR1 fusion gene transcripts, as shown by RT-PCR ( Figure 3F ).