Vega González, JesúsCortés Toro, José AntonioMarquina Ospina, GloriaTorre Serrano, Montserrat de laColino Gallardo, Ana MaríaBergillos Giménez, ReyesHernández Martínez, DesiréGarcía Egido, AlejandroAlarcón García, LorenzoPlaza Hernández, José CarlosOrtega Medina, Luis2025-04-222025-04-222025-04-10Vega-Gonzalez, J., Toro, J. A. C., García, E. L., Ospina, G. M., Serrano, M. T., Gallardo, A. M. C., Giménez, R. B., Martínez, D. H., Egido, A. G., García, L. A., Nielsen, L., Plaza, J. C., & Medina, L. O. (2025). EWSR1::SSX1 Fusion-Driven Synovial Sarcoma: A Case Presentation and Review of the Literature. Genes, chromosomes & cancer, 64(4), e70048. https://doi.org/10.1002/gcc.700481045-225710.1002/gcc.70048https://hdl.handle.net/20.500.14352/119542According to the 5th edition of the WHO Classification of Soft Tissue and Bone Tumors, the diagnosis of synovial sarcoma relies on morphology, immunohistochemistry, and the detection of a specific fusion involving the SS18 gene with a member of the SSX gene family. However, few cases of synovial sarcoma that do not harbor such molecular alterations have been recently reported. We present the case of a patient with a diffuse pleural mass and pleural effusion that showed in a core needle biopsy a spindle cell neoplasia morphologically suggestive of synovial sarcoma. An SS18 break-apart FISH was performed with a negative result. Afterwards, an EWSR1::SSX1 fusion was detected by next-generation sequencing. There is scarce literature on non-SS18 fusion-driven synovial sarcomas, and no study has evaluated whether these novel molecular alterations have a relevant clinical impact on patients beyond the diagnostic value.engjournal article1098-2264https://doi.org/10.1002/gcc.70048https://onlinelibrary.wiley.com/doi/10.1002/gcc.70048restricted access616-006.3-04EWSR1pleuraSSX1synovial sarcomaCiencias Biomédicas32 Ciencias Médicas