case_images: PMC9677308_01
case_images: Abdominal ultrasound showing a heterogeneous right kidney (A) (white arrow)
  with a large, irregular, heterogeneous tissue mass at its upper and middle
  pole, containing areas of central necrosis (A) (red arrow), and
  calcifications (B) (yellow arrow).
case_images: 10.1177_2333794X221112637-fig1.jpg
case_images: PMC9677308_01_10.1177_2333794X221112637-fig1.jpg
case_images: fig1-2333794X221112637
case_images: An ultrasound was performed and showed a right retroperitoneal mass with a right renal origin, heterogeneous, with areas of central necrosis and calcifications (Figure 1).
case_images: Axial (A and B) and coronal (C) sections of an abdominal MRI scan showing the
  presence of a large right retroperitoneal tumor process occupying the right
  renal compartment in hypo T1 signal (A) with heterogeneous T2 signal (B),
  containing areas of necrosis and enhancing after Gadolinium injection
  (C).
case_images: 10.1177_2333794X221112637-fig2.jpg
case_images: PMC9677308_01_10.1177_2333794X221112637-fig2.jpg
case_images: fig2-2333794X221112637
case_images: T2 signal, T1 hyposignal, diffusion restriction, containing necrotic areas, and heterogeneously enhancing after Gadolinium injection (Figure 2). This process encompasses almost the entire kidney with capsular effraction and pyelocalic dilatation, it pushes back the adjacent digestive and vascular structures, responsible for a voluminous endoluminal thrombus of the right renal vein, extended to the inferior vena cava and to the right atrium and associated with lombo-aortic adenopathies (Figure 3), evoking in the first place a sarcoma.
case_images: Axial (A) and coronal (B) T2 sequences showing reflow of adjacent digestive
  and vascular structures (white arrow) and a Voluminous endo-luminal thrombus
  of the right renal vein, extended to the IVC and right atrium (yellow
  arrow).
case_images: 10.1177_2333794X221112637-fig3.jpg
case_images: PMC9677308_01_10.1177_2333794X221112637-fig3.jpg
case_images: fig3-2333794X221112637
case_images: T2 signal, T1 hyposignal, diffusion restriction, containing necrotic areas, and heterogeneously enhancing after Gadolinium injection (Figure 2). This process encompasses almost the entire kidney with capsular effraction and pyelocalic dilatation, it pushes back the adjacent digestive and vascular structures, responsible for a voluminous endoluminal thrombus of the right renal vein, extended to the inferior vena cava and to the right atrium and associated with lombo-aortic adenopathies (Figure 3), evoking in the first place a sarcoma.
case_images: Axial sections of thoracic CT in parenchymal window (A) and mediastinal
  window (B) showing a metastatic pulmonary nodule (yellow arrow),
  subcutaneous emphysema dissecting the right cervical and thoracic soft
  tissues (red arrow), and left pleurisy of small to moderate volume (white
  arrow).
case_images: 10.1177_2333794X221112637-fig4.jpg
case_images: PMC9677308_01_10.1177_2333794X221112637-fig4.jpg
case_images: fig4-2333794X221112637
case_images: A thoracic CT scan was performed for a workup of extension and showed the presence of secondary pulmonary nodules with pleurisy (Figure 4).
case_images: (A) Clusters of round cells with reduced cytoplasm and finely nucleated
  hyperchromatic with no obvious signs of differentiation. (B) Cytoplasmic
  staining of tumor cells by anti-WT1 antibody. (C) Absence of anti-LCA
  antibody staining.
case_images: 10.1177_2333794X221112637-fig5.jpg
case_images: PMC9677308_01_10.1177_2333794X221112637-fig5.jpg
case_images: fig5-2333794X221112637
case_images: An echo-guided biopsy was performed and the anatomopathological study showed cytoplasmic labeling of the tumor cells by the anti-WT1 antibody, confirming the diagnosis of nephroblastoma (Figure 5).