Hasdemir P.S.Aliyeva A.Mavili S.Göksel G.2024-07-222024-07-22202413059319http://akademikarsiv.cbu.edu.tr:4000/handle/123456789/11290Extraosseous Ewing’s sarcoma is an extremely rare tumor. In the literature, intestinal Ewing’s sarcoma was reported in 20 cases, and omental Ewing’s sarcoma was reported in only two cases. In this case report, we report a 23-year-old female who presented with the complaint of diffuse abdominal pain. Abdominal ultrasound and whole-body computed tomography revealed a mass starting from the adnexal area and extending between the intestinal loops. Serum levels of tumor markers were high. The serum levels of carbohydrate antigen-125 (CA-125) and carcinoembryonic antigen-19.9 (CA-19.9) were high (427.5 U/mL and 67.9 U/mL, respectively). Laparotomic exploration was performed with the preliminary diagnosis of an adnexal mass, and a mass originating from the small intestine meso and completely covered by the omentum was excised. Histological evaluation reported intestinal and omental origin of Ewing’s sarcoma. This case highlights the importance of rare extraosseous Ewing’s sarcoma, which should be included in the differential diagnosis of a young female with intra-abdominal mass. © 2024 Galenos Publishing House. All rights reserved.EnglishCD56 antigenCD99 antigencyclophosphamidedactinomycinetoposidegranulocyte colony stimulating factorifosfamidesynaptophysinvimentinvincristineabdominal painadnexa diseaseadultArticlebleedingcancer chemotherapycase reportclinical articlecomputer assisted tomographycontrast enhancementdiagnostic errorend to end anastomosisEwing sarcomaewrs1 genefemalefluorescence in situ hybridizationgenegene rearrangementhistopathologyhumanhuman tissueimmunohistochemistryintestinal sarcomalaparotomyliver metastasislymph node metastasislymph vessel metastasismesenterymetastasisneutropenianuclear magnetic resonance imagingparacentesisperitoneum metastasissystemic diseasetumor necrosistumor volumewhole body CTyoung adultArticle10.4274/BMJ.galenos.2023.2022.3-10