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Ewing's sarcoma/PNET of the kidney

Case contributed by Dr Imran Ahmad Khan


Moderate left flank pain for the past two weeks.

Patient Data

Age: 40 years
Gender: Female

Large heterogeneous left renal mass. Variable internal necrotic areas are seen. Intermediate level of internal vascularity is present. No calcification. No direct invasion/ involvement of any adjoining structure.


Large irregular, heterogeneous, mildly enhancing left renal mass centered on lower pole and anterior cortex, with the posterior cortex stretched around the lesion. The upper pole calyces are moderately dilated while the middle and lower pole calyces are distorted. Multiple internal necrotic areas are present. No calcification or hemorrhage. The left main renal vein and IVC are patent and show no tumor thrombus. No evidence of direct invasion of any adjoining structures.

Case Discussion

A diagnosis of renal cell carcinoma was made based on imaging. Complete staging showed stage II tumor, T2 N0 M0.  A radical left nephrectomy performed. 

Histological examination was consistent with PNET/Ewing's sarcoma, with the tumor composed of nests and sheets of loosely cohesive monotonous small round cells with minimal cytoplasm and small round hyperchromatic to vesicular nuclei with inconspicuous nucleoli. Mitotic figures are numerous 2-9/HPF. Apoptotic cells are also noted. Foci of perivascular condensation of tumor cells and rosette formation noted. Areas of lymphovascular invasion seen.

Primary Ewing's sarcoma/primitive neuroectodermal tumor (PNET) of the kidney is extremely rare. It is a high grade tumor with an aggressive course and a poor prognosis.

It is a mesenchymal tumor occurring mainly in adults, according to the WHO classification of the tumors of the kidney.

Clinical presentation and imaging findings are non-specific and the diagnosis is made by histopathology and immunohistochemistry.

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