7 Primary Pancreatic Ewing Sarcoma in a Pediatric Patient: A Rare Small Round Blue Cell Tumor of the Pancreas

This is the authors' abstract. We don't add key points for this paper.

Introduction/Objective Ewing sarcoma is an aggressive malignant small round blue cell tumor that predominantly affects children and adolescents, typically arising in bone or occasionally in soft tissue. It is characterized by chromosomal translocations involving the EWSR1 gene, most commonly t(11;22)(q24;q12). Extraosseous disease is uncommon, and primary pancreatic involvement is extremely rare. Pediatric pancreatic tumors are themselves rare and include pancreatoblastoma, pancreatic neuroendocrine tumors, and non-Hodgkin lymphoma, making accurate diagnosis challenging due to overlapping clinical and histologic features. Methods/Case Report We describe a 9-year-old boy who presented with abdominal pain and a palpable abdominal mass. Imaging studies identified a 4.5 cm lesion located in the pancreatic body. Histopathologic evaluation showed sheets of uniform small round cells with minimal cytoplasm and a high nuclear-to-cytoplasmic ratio. Immunohistochemical staining demonstrated strong membranous CD99 expression along with nuclear FLI-1 positivity. Molecular testing detected an EWSR1 gene rearrangement, confirming the diagnosis of primary pancreatic Ewing sarcoma. Results NA Conclusion Primary pancreatic Ewing sarcoma is exceedingly rare in children. Recognition of its characteristic histologic, immunohistochemical, and molecular findings is vital for accurate diagnosis and appropriate treatment planning. This case emphasizes the importance of considering Ewing sarcoma in the differential diagnosis of pediatric pancreatic small round blue cell tumors.