Diagnosis of extraskeletal Ewing sarcoma in the omentum: A case study with molecular and pathological insights

Primitive neuroectodermal tumors (PNETs), particularly Ewing sarcoma (EES), are rare, aggressive malignancies typically observed in children and adolescents. While they commonly arise in skeletal locations, about 20–30% of cases occur in extraskeletal sites, complicating diagnosis. Extraskeletal Ewing sarcoma (EES) involving the omentum is exceedingly rare, with only a few documented cases. This report presents a case of EES localized to the omentum in an adult patient, underscoring the diagnostic challenges and importance of early identification. A 34-year-old Bahraini male presented with progressive abdominal distention, weight loss, fever, night sweats, and flank pain. Imaging revealed omental thickening and diffuse ascites. A laparoscopic biopsy and histopathological analysis confirmed the diagnosis of EES, with molecular confirmation of the EWSR1 translocation (t(11;22)(p13;q12)). EES in the omentum presents diagnostic challenges, often mimicking conditions such as peritoneal carcinomatosis and tuberculosis. This case emphasizes the critical role of integrating clinical, radiological, histological, and molecular data to accurately diagnose rare tumors like EES, and the importance of recognizing unusual presentations to avoid misdiagnosis. EES should be considered in the differential diagnosis of abdominal masses, particularly in patients with unexplained systemic symptoms and imaging findings suggestive of malignant processes. A comprehensive diagnostic approach, including molecular analysis, is crucial for accurate diagnosis and effective management.