Pathogenesis of Ewing sarcoma: Existing and emerging trends

Background: Ewing sarcoma (ES) of head & neck is uncommon in Indian subcontinent and poses challenge in diagnosis. This review is intended to comprehend clinical features, cell of origin, gene fusions, molecular pathogenesis and immunohistochemical markers (IHC) of ES to succour in contemplating its diagnosis. Methods: A literature search of the electronic databases of PubMed, Scopus and Web of Science (1865-2020) was conducted and handsearching of reference articles was done. Search strategy used MESH keywords like 'Ewing's sarcoma', 'PNET' and 'round cell tumor', 'gene fusions of ES', etc. Results: ESs are common in younger age group and it involves mostly mandible among head & neck region. Clinical and radiological features are variable. ES has hallmark chromosomal translocation of EWSR1 and FLI1 genes. But in recent times many other genetic fusions have been identified with similar clinical phenotype. It has few cells of origin but not easy to find the archetype. Conclusion: The author hopes that this review has abridged all the facts related to puzzling Ewing sarcoma by analysing newer gene fusions of all the head & neck ES cases reported in India and correlate them with clinical phenotype, enabling the best therapeutic approach.