Primitive neuroectodermal tumor (PNET)/Ewing sarcoma of kidney: A rare case report of three cases

Abstract

Primitive neuroectodermal tumor (PNET) / Ewing sarcoma of kidney are rare aggressive tumor with poor prognosis. It occurs in young adults generally in 2nd to 3rd decade of life We report three cases of PNET/Ewing sarcoma of kidney in patients of age 25and 35 years with complain of hematuria and abdominal pain .CT scan revealed heterogeneously enhancing lesion in kidney and we received radical nephrectomy specimen with variegated appearance on gross. Microscopic examination showed tumor with malignant cells in sheets and pseudorosettes .The diagnosis was given as PNET/ES and was confirmed with immunohistochemistry. Renal PNET/ES is a member of Ewing sarcoma family. They are rare tumor originating from the neural crest and are more aggressive than PNET at any other site. The presence of Homer Wright rosettes is less common in extra-osseous Ewing sarcoma and their presence is a sure diagnosis of PNET/ES. The differential diagnosis for these small round cell tumor of kidney other than PNET include malignant lymphoma, renal neuroblastoma,,embryonalrhanbdomyosarcoma, wilms tumor. The immunohistochemical marker CD99 positivity is diagnostic. Other markers positive are S-100, vimentin and NSE (neuron specific enolase). Histopathology and immunohistochemistry remains gold standard for confirming the diagnosis.