RESUMEN
We report a 32-year-old male who presented with huge [17x10.5x5 cm] right kidney with metastasis in the liver and retroperitoneal lymph nodes. Histological, detailed immunohistochemical studies and electron microscopic examinations were performed. Microscopy revealed small to intermediate sized cells with hyperchromatic nuclei, scanty cytoplasm, abundant mitosis with no pseudorossete formation. Immunohistochemical study revealed positive staining of the tumor cells for S100, neurofilaments, neuron specific enolase, vimentin and myoglobin. Primitive neuroectodermal tumors are rare malignant round cell tumors of the kidney. A correct diagnosis can be made on light microscopic features, and by immunohistochemically positive staining for more than one neural marker. This neoplasm should be differentiated from other renal neoplasms composed of small round cells