Primary Ewing’s Sarcoma of the Kidney Mimicking Renal Cell Carcinoma With Widespread Metastasis: A Case Report and a Brief Review of the Literature

Figure 1. Axial NCCT image revealed a large heterogeneous mass in the left renal fossa (A, long arrow), showing neovascularization on arterial phase images (B, short arrow). The mass demonstrated heterogeneous post-contrast enhancement with non-enhancing necrotic areas within on the venous phase (C, D, long arrow). Heterogeneous enhancing tumor thrombosis was seen in the IVC and left renal vein (C, D, black arrows). NCCT: non-contrast computed tomography; IVC: inferior vena cava

Figure 2. T2-HASTE coronal and axial images reveal a large heterogeneously hyperintense mass lesion in the left renal fossa with cystic areas (A, B; long arrow). The mass shows significant diffusion restriction (D, long arrow) with corresponding low apparent diffusion coefficient (ADC) values (E, long arrow). A few hyperintense areas on Dixon fat-suppressed images (C, short arrow) exhibit blooming on TRUFI (F, short arrow), indicating hemorrhage. HASTE: half-Fourier acquisition single-shot turbo spin-echo; TRUFI: true fast imaging with steady-state free precession

Figure 3. Coronal reformatted MIP MR angiography images reveal a mass in the left renal fossa showing marked neovascularity (A, long arrow) and supplied by the left renal artery (B, long arrow). Coronal reformatted MIP venography images demonstrate a hypointense thrombus in the inferior vena cava (IVC) (C, long arrow) and left renal vein (C, short arrow). Axial post-contrast T1FS images show heterogeneous post-contrast enhancement of the mass (D, E, long arrow) and heterogeneously enhancing tumor thrombus in the IVC and left renal vein (D, E, short arrow). A thick enhancing capsule is noted at the periphery of the lesion on the sagittal post-contrast T1FS image (F, long arrow). MIP: maximum intensity projection; FS: fat-saturated

Figure 4. Histopathological examination (HPE) shows small ovoid tumor cells with irregular hyperchromatic nuclei and scant cytoplasm (A, H&E, 400X). Immunohistochemical (IHC) staining reveals synaptophysin positivity (B, 400X).

Figure 5. An 18F-FDG whole-body PET/CT scan reveals no lesions in the operative bed but shows FDG-avid hypodense perisplenic deposits (A, B, arrow), FDG-avid hypodense metastatic deposits in the liver (C, D, arrow), and an FDG-avid lytic lesion in the right ischium (E, F, arrow). F18-FDG: fluorine-18 fluorodeoxyglucose; PET: positron emission tomography

Figure 6. Ultrasound scan images of the left orbit (A, B) reveal a heterogeneously hypoechoic retro-bulbar mass lesion (arrow) showing vascularity on color Doppler with a low resistance waveform on spectral Doppler. Ultrasound of the abdomen and pelvis (C, D) shows a large heterogeneously hyperechoic lesion in the left renal fossa, abutting the spleen supero-laterally and the left lobe of the liver medially (C, arrow). Additionally, multiple round to oval hyperechoic focal lesions diffusely involving the liver parenchyma, most with peripheral halos, are observed (D). These findings are consistent with retro-bulbar, hepatic, and left renal fossa metastases.

Figure 7. MRI images of the left orbital region (A-E) show a well-defined soft tissue lesion in the extra-conal compartment of the supero-lateral aspect of the left orbit. The lesion appears hyperintense on T2-weighted (A, C, asterisk) and FLAIR (B, asterisk) images, isointense to gray matter on T1-weighted images (D), and demonstrates diffusion restriction (E). There is an abnormal signal with erosions of the adjacent lateral wall of the left orbit, the lesser wing of the sphenoid, and the spheno-temporal buttress (A-D, long arrow), along with associated extra-dural soft tissue (A-C, short arrow). Heterogeneous enhancement of the orbital and extra-dural soft tissue lesions, as well as the involved bones, is noted on T1 fat-saturated images (F-H). Post-contrast fat-saturated axial FLAIR image (I) at the level of the body of the lateral ventricles also shows multiple abnormal calvarial lesions with adjacent soft tissue components (small arrows) and enhancing pachymeningeal thickening (long arrow). These findings are consistent with multiple skeletal metastases and a left extra-conal orbital soft tissue mass. FLAIR: fluid-attenuated inversion recovery