Ewing sarcoma

Ewing sarcoma is more common in males (1.6 male:1 female) and usually presents in childhood or early adulthood, with a peak at about 19 years of age. 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. Signs and symptoms include intermittent fevers, anemia, leukocytosis, increased sedimentation rate, and other symptoms of inflammatory systemic illness. ==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. A 2015 continuative study discovered that the Ewing sarcoma susceptibility gene EGR2, which is located within the chromosome 10 susceptibility locus, is regulated by the EWSR1-FLI1 fusion oncogene via a GGAA-microsatellite. A 2018 GWAS (Machiela, et al, 2018) Other translocations are at t(21;22) and t(7;22). Ewing sarcoma cells are positive for CD99 and MIC2, ==Diagnosis==

of a metastatic Ewing sarcoma with the characteristic cytoplasmic clearing on H&E staining, which was showing to be PAS positive The definitive diagnosis is based on histomorphologic findings, immunohistochemistry and molecular pathology. Ewing sarcoma is a small-blue-round-cell tumor that typically has a clear cytoplasm on H&E staining, due to glycogen. The presence of the glycogen can be demonstrated with positive PAS staining and negative PAS diastase staining. The characteristic immunostain is CD99, which diffusely marks the cell membrane. However, as CD99 is not specific for Ewing sarcoma, several auxiliary immunohistochemical markers can be employed to support the histological diagnosis. Morphologic and immunohistochemical findings are corroborated with an associated chromosomal translocation, of which several occur. The most common translocation, present in about 90% of Ewing sarcoma cases, is t(11;22)(q24;q12), which generates an aberrant transcription factor through fusion of the EWSR1 gene with the FLI1 gene. The pathologic differential diagnosis is the grouping of small-blue-round-cell tumors, which includes lymphoma, alveolar rhabdomyosarcoma, and desmoplastic small round cell tumor, among others. 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. ==Treatment==

Almost all people receive multidrug chemotherapy (most often vincristine, doxorubicin, cyclophosphamide, ifosfamide, and etoposide), as well as local disease control with surgery and/or radiation. An aggressive approach is necessary because almost all people with apparently localized disease at the time of diagnosis actually have asymptomatic metastatic disease. The surgical resection may involve limb salvage or amputation. Complete excision at the time of biopsy may be performed if malignancy is confirmed at the time it is examined. Treatment lengths vary depending on location and stage of the disease at diagnosis. Radical chemotherapy may be as short as six treatments at three-week cycles, but most people undergo chemotherapy for 6–12 months and radiation therapy for 5–8 weeks. Radiotherapy has been used for localized disease. The tumor has a unique property of being highly sensitive to radiation, sometimes acknowledged by the phrase "melting like snow", but the main drawback is that it recurs dramatically after some time. Antisense oligodeoxynucleotides have been proposed as possible treatment by down-regulating the expression of the oncogenic fusion protein associated with the development of Ewing sarcoma resulting from the EWS-ETS gene translocation. In addition, the synthetic retinoid derivative fenretinide (4-hydroxy(phenyl)retinamide) has been reported to induce high levels of cell death in Ewing sarcoma cell lines in vitro and to delay growth of xenografts in in vivo mouse models. In most pediatric cancers including sarcoma, proton beam radiation (also known as proton therapy) delivers an equally effective dose to the tumor with less damage to the surrounding normal tissue compared to photon radiation. ==Prognosis==

Staging attempts to distinguish people with localized from those with metastatic disease. The most common areas of metastasis are the lungs, bone and bone marrow with less common areas of metastasis being the lymph nodes, liver, and brain. The presence of metastatic disease is the most important prognostic factor in Ewing sarcoma, with the 5-year survival rate being only 30% when metastasis is present at the time of diagnosis, compared to a 70% 5-year survival rate with no metastasis present. Prior to the use of multi-drug chemotherapy, long-term survival was less than 10%. The development of multi-disciplinary therapy with chemotherapy, irradiation, and surgery has increased current long-term survival rates in most clinical centers to greater than 50%. However, some sources state it is 25–30%. Retrospective research showed that two chemokine receptors, CXCR4 and CXCR7, can be used as molecular prognosis factors. People who express low levels of both chemokine receptors have the highest odds of long-term survival with >90% survival at five years post-diagnosis versus <30% survival at five years for patients with very high expression levels of both receptors. A recent study also suggested a role for SOX2 as an independent prognostic biomarker that can be used to identify patients at high risk for tumor relapse. ==Epidemiology==

Ewing sarcomas represent 16% of primary bone sarcomas. In the United States, they are most common in the second decade of life, It is uncommon in patients younger than 5 years and older than 30 years. In the United Kingdom, an average of six children per year are diagnosed; mainly males in early stages of puberty. With occurrences primarily arising in older children and teenagers, one causal theory is puberty, e.g. its rapid growth spurts making bone tissue more cancer susceptible during development years. A grouping of three unrelated teenagers in Wake Forest, North Carolina, have been diagnosed with Ewing sarcoma. All three children were diagnosed in 2011 and all attended the same temporary classroom together while the school underwent renovation. A fourth teenager living nearby was diagnosed in 2009. The odds of this grouping are considered significant. Ewing sarcoma occurs about 10- to 20-fold more commonly in people of European descent compared to people of African descent. == References ==