KjG The Korean Journal of Gastroenterology Korean J Gastroenterol 1598-9992 2233-6869 Korean Society of Gastroenterology 10.4166/kjg.2013.62.4.253 kjg-62-253 Image of the Month Retroperitoneal Extraskeletal Ewing's Sarcoma LeeSi Hyung JangByung Ik Department of Internal Medicine, Yeungnam University College of Medicine, Daegu, Korea Correspondence to: Byung Ik Jang, Department of Internal Medicine, Yeungnam University College of Medicine, 170 Hyeonchung-ro, Nam-gu, Daegu 705-717, Korea. Tel: +82-53-620-3830, Fax: +82-53-654-8386, E-mail: jbi@med.ac.kr 10 2013 04 10 2013 624 253 255 Copyright © 2013 Korean Ophthalmological Society 2013 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. References Maheshwari AV Cheng EY Ewing sarcoma family of tumors J Am Acad Orthop Surg 2010 1894107 Tefft M Vawter GF Mitus A Paravertebral "round cell" tumors in children Radiology 1969 9215011509 Downing JR Head DR Parham DM Detection of the (11;22)(q24;q12) translocation of Ewing's sarcoma and peripheral neuroectodermal tumor by reverse transcription polymerase chain reaction Am J Pathol 1993 14312941300 Raney RB Asmar L Newton WA Jr Ewing's sarcoma of soft tissues in childhood: a report from the Intergroup Rhabdomyosarcoma Study, 1972 to 1991 J Clin Oncol 1997 15574582 Murtaza B Saeed S Khan NA Retroperitoneal masses: different clinical scenarios J Ayub Med Coll Abbottabad 2008 20161164 Kennedy JG Eustace S Caulfield R Fennelly DJ Hurson B O'Rourke KS Extraskeletal Ewing's sarcoma: a case report and review of the literature Spine (Phila Pa 1976) 2000 2519961999 Lee WS Kim YH Chee HK Multimodal treatment of primary extraskeletal Ewing's sarcoma of the chest wall: report of 2 cases Cancer Res Treat 2009 41108112 El Weshi A Allam A Ajarim D Extraskeletal Ewing's sarcoma family of tumours in adults: analysis of 57 patients from a single institution Clin Oncol (R Coll Radiol) 2010 22374381 Figures

Initial CT scan. (A) Pre-enhance axial image shows 3.7 cm sized cystic mass without solid component. (B) This mass is not enhanced after contrast administration.

Follow-up CT scan after 6 months. (A) The mass has enlarged to about 6 cm in size. (B) Contrast-enhanced abdominal CT scan shows 6 cm sized heterogenous enhancing mass with central low attenuation at retrocaval area.

(A) Microscopic finding of ultrasound guided biopsy shows small round neoplastic cells with irregular nuclei and sparse cytoplasm (H&E,×400). (B) This tumor cells shows strong diffuse membrane immunohistochemical reactivity with CD99 antibodies (CD 99, ×400).