Objective: Ewing's sarcoma/Primitive neuroectodermal tumor (ES/PNET) is an extraordinarily rare primary tumor in the kidney. We re-port herein the clinical, histological, and immunohisto-chemical features of a primary renal ES/PNET.
Methods: A 19-year old male referred a two weeks history of constant, colic, left flank pain, and fever. A left radical nephrectomy was performed. Gross pathologic examination showed pink-tan, lobulated solid tumor, localized at the superior pole.
Results: Histologically, the tumor was solid with necrosis. The neoplastic cells showed a small amount of clear cytoplasm, and had vesicular nuclei with small nucleoli. Immunohistochemical studies showed strongly and diffusely positive staining for CD99 in a membranous pattern.
Conclusions: This case represents a typical ES/ PNET affecting a young male patient. Adequate diagnosis is important because this neoplasm has an aggressive behaviour.