label: Ewing Sarcoma of Bone
label_lc: ewing sarcoma of bone
description: A small round cell bone tumor that lacks morphologic, immunohistochemical, and electron microscopic evidence of neuroectodermal differentiation.  It represents one of the two ends of the spectrum called Ewing sarcoma/peripheral neuroectodermal tumor.  It often affects the diaphysis or metaphyseal-diaphyseal portion of long bones.  Clinical findings include pain and a mass in the involved area.  Fever, anemia, leukocytosis, and an increased sedimentation rate are often seen.  X-ray examination reveals osteolytic lesions.  The prognosis depends on the stage, anatomic location, and size of the tumor.