Primitive neuroectodermal tumor of bone

We report a rare case of primitive neuroectodermal tumor (PNET) of bone.A 25-year-old woman complained of pain and swelling in her left upper leg. An elastic hard mass, which was tender and hot was palpable. Roentgenographically, an irregularly marginated radiolucent area with cortical destruction at the epi-metaphysis of the left tibia was noted. On microscopic examination, the tumor was made up of sheets of closely packed round to ovoid cells. Apparent structual features such as rosette formation were absent. Glycogen granules were negative for PAS stain. Immunohistochemically, neural markers including NSE, myogenic markers, vascular markers were all negative except focally weakly positive for MIC-2 gene product.This tumor is thought to be poorly differentiated and appears to have characteristics between Ewing's sarcoma and PNET.