Ewing sarcoma of the kidney: a rare entity

Abstract

Ewing sarcoma and primitive peripheral neuroectodermal tumor (PNET) are high-grade malignant tumors typically found in children and adolescents. These tumors belong to the family of small round cell tumors and are of neuroectodermal origin. Primary Ewing sarcoma of the kidney is rare and because of that is an infrequent differential diagnosis in urologic malignancies. Renal PNET mostly presents with nonspecific symptoms such as hematuria and abdominal pain. The imaging findings are uncharacteristic. The diagnosis is based on the histology, immunohistochemistry, and molecular pathologic findings. Once PNET has been diagnosed, multimodal treatment is indicated. Despite all treatment options, the prognosis of those with metastatic disease is poor.

Figure 1

(a) Sagittal ultrasound image of the right kidney shows a large mass replacing the upper pole of the right kidney (arrow). The echotexture is similar to renal parenchyma with mild internal heterogeneity and a few cystic spaces. (b) Sagittal ultrasound image with Doppler shows internal vascularity (arrows) within the large mass replacing the superior pole of the right kidney.

Figure 2

(a) Axial contrast-enhanced multidetector computed tomography (MDCT) image of the upper abdomen reveals a large mass of heterogeneous attenuation replacing the midportion and superior pole of the right kidney (star). Mass has broken into the hepatorenal space (vertical arrow) and invaded the right liver. A metastatic pericaval lymph node is seen (horizontal arrow). (b) Axial contrast-enhanced MDCT image shows a large lobulated component of the renal mass invading the right liver (horizontal arrow). An enlarged metastatic left gastric lymph node is also noted (vertical arrow).

Figure 3

Coronal reconstructed CT image shows large lobulated mass of heterogenous attenuation invading the right liver (horizontal arrow). The right adrenal gland is expanded and completely replaced by the tumor (vertical arrow).

Figure 4

((a) and (b)) Axial CT scan images of the chest reveal small subcentimeter nodules in the right lower lobe (arrow in (a)) and left upper lobe nodule (arrow in (b)), suspicious for pulmonary metastases.

Figure 5

(a) A Diff-Quick stained, air-dried direct smear of Ewing's sarcoma shows a monotonous population of tumor cells with high nuclear: cytoplasmic ratio. Scattered apoptotic cells in the background give an appearance of “double population.” (b) Pap-stained, Alcohol fixed direct smear of Ewing's/PNET shows a malignant small round cell tumor, singly and in loosely cohesive clusters. Numerous apoptotic cells are present. The tumor cells demonstrate mild to moderate nuclear pleomorphism, irregular nuclear contour with fine chromatin, and inconspicuous nucleoli. (c) Pap-stained, alcohol fixed direct smear of Ewing's/PNET shows a malignant small round cell tumor, singly and in loosly cohesive clusters. Numerous apoptotic cells are present. The tumor cells demonstrate mild to moderate nuclear pleomorphism, irregular nuclear contour with fine chromatin, and inconspicuous nucleoli.