Ewing's Sarcoma (ES)

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The destructive nature of this lesion, the age and gender of the patient, and the location are all consistent with the behavior of Ewing's sarcoma; for that reason, it should be on the differential diagnosis. The histology, however, is not supportive of ES.

Ewing sarcoma is a malignant neoplasm primarily of bone constituting 6-8% of primary bone malignancies. It is the third most common such neoplasm generally speaking after osteosarcoma and chondrosarcoma. It is of unknown histogenesis, but immunohistochemistry stains of this neoplasm suggest that the cells are of neural crest origin. Extraskeletal (soft tissue) Ewing's sarcoma is also described, but not commonly. Up to 90% of these cases show reciprocal translocation between chromosomes 11 and 22. Clinically, this neoplasm usually presents with pain and swelling of a short duration. Soft-tissue swelling overlying the bone is often present because the tumor perforates the bone in a soft-tissue mass. The most common bones affected by this neoplasm are the long bones, pelvis and ribs; the jaw bones are much less commonly affected, and of the two, the mandible is more commonly affected than the maxilla. It has a slight predilection for occurrence in males and has a peak incidence in children 10 to 15 years old. It is by far more common in Caucasians and is very rare in blacks and Asians. Radiographically, it usually presents as an ill-defined radiolucency with a moth-eaten appearance in some cases. The typical onionskin reaction of the periosteal reaction is common in the long bones and less common in the jaw bones. Histologically, it is characterized by sheets of round blue cells with hyperchromatic nuclei and clear cytoplasm. Immunohistochemistry staining demonstrates the presence of the cell surface antigen CD99, but other neoplasms also express this marker.