Radiology-pathology conference: primary perinephric and renal extraosseous Ewing's sarcoma.

Ewing's sarcoma/primitive neuroectodermal tumor is a rare entity belonging to a family of neoplasms of neuroectodermal origin. These highly aggressive neoplasms overwhelmingly affect children and young adults. A quarter of Ewing's sarcomas occur principally in the soft tissues with primary involvement of the perinephric fat and kidney being exceptionally rare. We present a 38-year-old man with primary Ewing's sarcoma of the perinephric fat and kidney diagnosed 2 years earlier who subsequently developed an infiltrating left renal and perinephric mass.