Retroperitoneal alveolar rhabdomyosarcoma intruding into spinal canal: A case report and literature review

Abstract

Background: Rhabdomyosarcoma (RMS) is the most frequent soft sarcoma in children and adolescents. Alveolar rhabdomyosarcoma (ARMS) is a relatively rare subtype that is characterized by aggressive behavior and an unsatisfactory prognosis. An ARMS can arise anywhere but most commonly occurs at extremity sites with a very small fraction in the retroperitoneum. The utility of 2-Deoxy-2-[fluorine-18]-fluoro-D-glucose (¹⁸F-FDG) positron emission tomography combined with computed tomography (PET/CT) remains to be established in ARMS.

Case report: A 3-year-old female child was accidentally found with a large left upper abdominal mass for a day. CT examination indicated a huge soft tissue mass 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. ¹⁸F-FDG PET/CT found a mass in the left retroperitoneum from the level of T12 to the left acetabulum, with the maximum standardized uptake value (SUV_max) of about 7.0, and a CT value of about 39 HU, invading the left L3-5 intervertebral foramina and protruding into the spinal canal, with unclear boundary with the spinal cord. Retroperitoneal tumor resection and the repair operation of vascular exploration were performed. An ARMS was confirmed by postoperative biopsy, immunohistochemical staining, and genetic detection with the rupture of the fork head in rhabdomyosarcoma (FKHR). The patient received chemotherapy and was in a good condition with no recurrence and obvious complications.

Conclusion: Retroperitoneal ARMS is rare and indicates a poor outcome with the potential to involve vital organs and intrude into the spinal canal. Accurate diagnosis and staging using PET/CT would contribute to better risk stratifications and appropriate treatment individually.

Keywords: 18F-FDG; PET/CT; alveolar rhabdomyosarcoma; case report; retroperitoneum; spinal canal intrusion.

Figure 1

Ultrasound images of retroperitoneal alveolar rhabdomyosarcoma (ARMS). (A) A heterogeneous hypoechoic area of about 13.8 × 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).

Figure 2

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.

Figure 3

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 (SUV_max) of about 7.0, the maximum layer of 8.8 × 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.

Figure 4

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) ×100]; (C) The fork head in rhabdomyosarcoma (FKHR) gene rupture was positive (fluorescence in situ hybridization) [magnification ×1000].