Ewing's sarcoma

Introduction

A malignant small round cell tumor found in young patients Age & location found in patients from 5-25 years of age ~50% are found in the diaphysis of long bones common locations include the femoral shaft, knee (distal femur and prox tibia), pelvis and proximal humerus Genetics 90% have t(11:22) translocation which leads to the formation of a fusion protein (EWS-FLI 1) Prognosis 60-70% long term survival with treatment only 40% long term survival with pelvis lesions only 15% long term survival if patient presents with metastasis to the lung

Symptoms

Presentation pain often accompanied by fever often mimics an infection Physical exam swelling and local tenderness

Imaging

Radiographs large destructive lesion in the diaphysis or metaphysis with a moth-eaten appearance  periosteal lifting may give "onion skin" or "sunburst" appearance Bone scan hot required as part of workup MRI often shows a large soft tissue component  CT chest is important to rule out mets to lungs (very common)

Labs

ESR is elevated WBC is elevated Anemia is common Bone marrow biopsy  required as part of workup for Ewing's to rule out metastasis to the marrow

Histology

Characteristic findings sheets of monotonous small cells  cells have scant cytoplasm  may have pseudo-rosettes (circle of cells with necrosis in center)  Immunostain CD99 reactivity

Treatment

Multimodality multistage chemotherapy and limb salvage resection preoperative chemotherapy given for 8-12 weeks followed by maintenance chemotherapy for 6-12 months after surgical resection  irradiation current trend towards surgical resection and away from irradiation due to high risk of irradiation-induced secondary malignancies situations where radiation can be used include  radiation alone for areas that cannot be resected (ie, large bulky pelvic tumors), in combination with local resection if surgical margins are close