Medical imaging
On conventional radiographs, typical findings of Ewing sarcoma consist of multiple confluent lytic bone lesions that have a "moth eaten" pattern due to permeative destruction of bone. There will also be a displaced periosteum as the new sub-periosteal layer of bone begins to grow on top of the tumor. This raised or displaced periosteum is consistent with the classic radiographic finding of the Codman triangle. The proliferative reaction of bone can also create delicate laminations constituting the periosteal layers and giving the radiographic appearance of an onion peel. Plain films add valuable information in the initial evaluation or screening. The wide zone of transition (e.g. permeative) is the most useful plain film characteristic in differentiation of benign versus aggressive or malignant lytic lesions. Magnetic resonance imaging (MRI) should be routinely used in the work-up of malignant tumors. It will show the full bony and soft tissue extent and relate the tumor to other nearby anatomic structures (e.g. vessels). Gadolinium contrast is not necessary as it does not give additional information over noncontrast studies, though some current researchers argue that dynamic, contrast-enhanced MRI may help determine the amount of necrosis within the tumor, thus help in determining response to treatment prior to surgery.Computed axial tomography (CT) can also be used to define the extraosseous extent of the tumor, especially in the skull, spine, ribs, and pelvis. Both CT and MRI can be used to follow response to radiation and/or chemotherapy.
It can occur anywhere in the body but most commonly in the pelvis and proximal long tubular bones, especially around the growth plates. The diaphyses of the femur are the most common sites, followed by the tibia and the humerus. Thirty percent are overtly metastatic at presentation, while 10–15% of people present with a pathologic fracture at the time of diagnosis. People usually experience extreme bone pain. Rarely, it can develop in the vagina.Signs and symptoms include intermittent fevers, anemia, leukocytosis, increased sedimentation rate, and other symptoms of inflammatory systemic illness.According to the Bone Cancer Research Trust (BCRT), the most common symptoms are localized pain, swelling, and sporadic bone pain with variable intensity. The swelling is most likely to be visible if the sarcoma is located on a bone near the surface of the body, but when it occurs in other places deeper in the body, like on the pelvis, it may not be visible. Genetics
Genetic exchange between chromosomes can cause cells to become cancerous. Most cases of Ewing sarcoma (about 85%) are the result of a defining genetic event; a reciprocal translocation between chromosomes 11 and 22, t(11,22), which fuses the Ewing Sarcoma Breakpoint Region 1 (EWSR1) gene of chromosome 22 (which encodes the EWS protein) to the Friend Leukemia Virus Integration 1 (FLI1) gene (which encodes Friend Leukemia Integration 1 transcription factor (FLI1), a member of the ETS transcription factor family) of chromosome 11.