• A rare tumor usually occurring in persons age 10-30 years
  • Patients usually present with pain and swelling of variable duration
  • Tumor most frequently located in distal femur and humerus, most are metaphyseal
  • Lesion may be sclerotic or mixed osteolytic/osteosclerotic
  • Permeative border and Codman’s triangle usually present
  • Soft tissue mass present in majority of cases
  • Histologically, sheets of small, round, blue cells observed
  • Appearance is similar to that of Ewing sarcoma, but differs from Ewing in that these cells produce osteoid
    • Use of Ewing immunohistochemical markers and evaluation for an 11:22 chromosomal translocation useful to eliminate a diagnosis of Ewing sarcoma