Primary Renal Ewings Sarcoma/Primitive Neuroectodermal Tumor (PNET) Of The Kidney, Can It Be Diagnosed On Imaging? A Case Report

Primary renal Ewing Sarcoma⁄primitive Neuroectodermal Tumor (PNET) of the kidney represents a rare aggressive pathologic entity seen in children and young adults. Here we present a case of a 46 year old woman who presented with bilateral lower quadrant abdominal pain and microscopic hematuria. Radiologic imaging demonstrated a large heterogeneous, vascular mass involving the upper pole of right kidney causing diffuse enlargement of kidney on ultrasound. Further imaging with a CT scan showed a moderately enhancing, diffusely infiltrating right upper pole mass with a tumor thrombus in right renal vein that extended into the infrahepatic portion of the inferior vena cava. An ultrasound guided biopsy of the lesion demonstrated a mass composed of neoplastic cells with primitive histomorphologic features and expression of vimentin, CD99 (MIC2), FLI–1, and BCL–2. The tumor was negative for WT–1, pankeratin, synaptophysin, chromogranin and CD45. FISH analysis showed a rearrangement of EWSR1 in 89% of cells. The patient subsequently underwent a right nephrectomy, IVC thrombectomy and regional lymph node dissection. The imaging features of renal PNET can be uncharacteristic and this tumor is mainly diagnosed based on the combination of pathological and radiological findings. By presenting this case report we expect to further knowledge on the imaging features and various options for preoperative diagnosis of renal ES⁄ PNET. Based on the case that we are presenting, we suggest diffuse infiltrative appearance of the tumor, moderate grade enhancement, peripheral areas of hemorrhage and necrosis and tumor thrombus in renal vein and IVC can suggest the imaging diagnosis of renal ES⁄PNET preoperatively.