CASE REPORT Extraosseous Ewing’s sarcoma of the pancreas Prithviraj Bose • Paari Murugan • Elizabeth Gillies • Jennifer L. Holter Received: 24 November 2010 / Accepted: 15 August 2011 / Published online: 3 September 2011 Ó Japan Society of Clinical Oncology 2011 Abstract The Ewing’s family of tumors (EFT) comprises a molecularly defined group of ‘‘small round blue cell tumors’’, consisting of Ewing’s sarcoma of bone (ESB), extraosseous Ewing’s sarcoma (EES), peripheral primitive neuroectodermal tumor (pPNET), and Askin’s tumor. Characteristic translocations that disrupt the EWSR1 gene located at 22q12 create novel fusion genes that are central to the pathogenesis. The EFT also shares certain clinical characteristics, such as a peak incidence during the teenage years, a tendency to spread rapidly, and responsiveness to the same chemotherapeutic regimens and radiation therapy. Nearly all patients have occult disseminated disease at diagnosis; hence, chemotherapy is routinely used. Improvements in multimodality treatment have had a dra- matic impact on outcomes. EES/pPNET has been reported in a variety of sites, including the pancreas, though this is extremely rare. We describe a case of pancreatic EES/ pPNET in a 35-year-old woman and provide a brief review of the relevant literature. Keywords Ewing’s sarcoma Á Extraosseous Ewing’s sarcoma Á Primitive neuroectodermal tumor Á PNET Á Pancreas Introduction Ewing’s sarcoma (ES) is the second most common pri- mary malignancy of bone, but can also arise in soft tis- sues (extraosseous Ewing’s sarcoma, EES) [1]. Primitive neuroectodermal tumor (PNET), formerly called neuro- epithelioma, was first described as a tumor of the ulnar nerve with the gross features of a sarcoma but composed of small round cells focally arranged as rosettes [2]. While ES and PNET may be distinguished by the absence of neural differentiation in the former and its presence in the latter, Ewing’s sarcoma of bone (ESB), EES, peripheral PNET (pPNET) and Askin’s tumor (malignant small-cell tumor of the thoracopulmonary region) are all now considered part of the Ewing’s family of tumors (EFT) [1]. Morphologically, the EFT are ‘‘small round blue cell tumors’’ [3]. ESB and EES are indistinguishable histo- logically. The vast majority of EFT strongly express CD99, a cell surface glycoprotein encoded by the MIC2 gene [4]. Over 85% of EFT harbor a reciprocal translo- cation involving the EWSR1 gene located at 22q12 and the FLI1 gene at 11q24 (t(11;22)(q24;q12)). This results in a fusion gene EWS-FLI1, whose product drives the growth of these tumors through deregulation of tran- scription and apoptosis. The FLI1 protein is a member of the ETS family of transcription factors. Analogous translocations accounting for most of the remaining cases fuse the EWSR1 gene to other ETS-family genes such as ERG, ETV1, E1AF or FEV [4]. P. Bose Á J. L. Holter Hematology/Oncology Division, Department of Internal Medicine, University of Oklahoma Health Sciences Center, 920 Stanton L Young Blvd, WP-2040, Oklahoma City, OK 73104, USA Present Address: P. Bose (&) Hematology/Oncology Division, Department of Internal Medicine, Virginia Commonwealth University/Massey Cancer Center, P.O. Box 980230, 1101 E Marshall St, Sanger Hall-6030, Richmond, VA 23298, USA e-mail: pbose@mcvh-vcu.edu; pbose@vcu.edu P. Murugan Á E. Gillies Department of Pathology, University of Oklahoma Health Sciences Center, 940 Stanton L Young Blvd, Oklahoma City, OK 73104, USA 123 Int J Clin Oncol (2012) 17:399–406 DOI 10.1007/s10147-011-0311-6