PMC9670135_01
Ultrasound images of retroperitoneal alveolar rhabdomyosarcoma (ARMS). (A) A heterogeneous hypoechoic area of about 13.8 x 10.4 cm in the left upper abdomen, with an unclear boundary with the left kidney. (B) Blood flow signal observed using color doppler flow imaging (CDFI).
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Blood flow signal could be observed using the color doppler flow imaging (CDFI) technique (Figure 1).
Enhanced computed tomography (CT) images of retroperitoneal ARMS. (A) A plain image with a CT attenuation value of about 47 HU; mottling calcification existing within the mass; (B) Arterial phase image with a CT attenuation value of about 50 HU; the mass supplied by branches of superior and inferior mesenteric arteries and areas of cystic degeneration and necrosis without enhancement existing within the mass; (C-F) venous phase image with a CT attenuation value of about 65 HU. Left renal vein reflux could be observed in the mass. The mass invaded the lumbar intervertebral foramen and compressed the left kidney, left abdominal bowel, and the inferior vena cava, and the abdominal aorta was also compressed and displaced to the right. The arrow illustrates the involvement of the inferior vena cava.
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Contrast-enhanced CT examination indicated a huge soft tissue mass, measuring 12.3 x 7.4 cm at the larger section, in the left retroperitoneum extending superiorly to the level of the left hilus renalis and inferiorly to the left acetabulum in the pelvic cavity, with intrusion into the lumbar foramens, compression and squeezing of the left kidney and left abdominal bowel, local compression and stenosis of the inferior vena cava, and the abdominal aorta was displaced to the right side by compression (Figure 2).
2-Deoxy-2-[fluorine-18]-fluoro-D-glucose (18F-FDG) positron emission tomography combined with computed tomography (PET/CT) images of retroperitoneal ARMS. (A) The whole-body maximum density projection showing hypermetabolic areas in the left retroperitoneum; (B) The axial images showing the concentrated distribution of radioactivity in soft tissue mass, with maximum standardized uptake value (SUVmax) of about 7.0, the maximum layer of 8.8 x 10.3 cm, and a CT value of about 39 HU; (C) The axial images showing invasion of the left L3-5 intervertebral foramen and protrusion into the spinal canal, with unclear boundary with the spinal cord (short arrows); (D) The axial images showing the involved retroperitoneal lymph nodes (dash arrows); (E) The coronal image showing the lesion extending from the level T12 to the left acetabulum.
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The tumor invaded the left L3-5 intervertebral foramina and protruded into the spinal canal, with an unclear boundary with the spinal cord (Figure 3). The abdominal cavity and retroperitoneum showed enlarged lymph nodes, with a SUVmax of about 6.4 and the largest size of about 2.0 x 3.0 cm.
Histopathological results. (A) Tumor cells were round or oval with hyperchromatic nuclei and nuclear fission (HE staining); (B) Cells forming patterns resembling pulmonary alveoli, and fibrous vascular tissue between the alveoli (HE stain) [magnification (A-B) x100]; (C) The fork head in rhabdomyosarcoma (FKHR) gene rupture was positive (fluorescence in situ hybridization) [magnification x1000].
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Histological results showed small round malignant cell with characteristic alveolar structures (Figures 4A,B). Fli-1 (-), Ki-67 (+60%), PAX-8 (+), CD56 (+), CgA (foci+), Desmin (+), Myo D1 (+), WT-1 (+), PD-1, S-100 (-), and PAX-5 (+). Fluorescence in situ hybridization revealed fork head in rhabdomyosarcoma (FKHR) rupture (Figure 4C).