Ewing's sarcoma

(James Ewing, 1866 - 1943, American pathologist), a malignant tumour of unknown histogenesis, perhaps originating from neuroectodermal tissue. Neuroblastoma of bone resembles Ewing's sarcoma clinically, radiographically and histologically, and these two tumours may be closely related. Most cases of Ewing's sarcoma are identified before the age of 30 years; pain is the most common presenting symptom. The sacrum and vertebral column, innominate bone, and bones of the lower extremity are the skeletal sites affected most frequently. The tumour is aggressive, as reflected by radiographic findings of poorly defined osteolysis, erosion of the cortex, periostitis and soft tissue mass. An onion-skin pattern, in which multiple layers of periosteal new bone appear, and the hair on end appearance, in which thin bone strands extend at right angles to the parent bone, are characteristic. In the vertebral body, bone destruction, collapse and fracture are common features. A large soft tissue mass with calcification may be present in the innominate bone. Bone scans reveal increased uptake of radionuclide in foci of tumour, and CT scanning and MR imaging also provide helpful information. CT scans define the extraosseous extent of Ewing's sarcoma, and MR imaging shows low signal intensity of the tumour in T1-weighted spin-echo images with high signal intensity in T2-weighted spin-echo images (Fig.1). Variants of the typical lesion include a large cell (atypical) type of Ewing's sarcoma, extraskeletal Ewing's sarcoma, neuroectodermal tumours and primitive neuroectodermal tumour (PNET) of bone.

DR/RB