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The report presents a 77-year-old man with abdominal pain and fever, with CT showing a 13 cm retroperitoneal tumor containing internal air and ileal involvement. After ileocecal resection, pathology confirmed DLS via MDM2 positivity, negative CD34/c-kit, and MDM2 amplification by FISH, followed by early favorable recovery then recurrence of a penetrating abscess progressing to an enterocutaneous fistula.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/retroperitoneal-dedifferentiated-liposarcoma-with-penetrating-abscess-formation-secondary-to-ileal-invasion-case-report/455207/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/retroperitoneal-dedifferentiated-liposarcoma-with-penetrating-abscess-formation-secondary-to-ileal-invasion-case-report/455207.png","ImageObject",300,407,{"name":92,"@type":93},"Mafia Boss","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-11-05","2026-09-30",true,{"@type":102,"interactionType":103,"userInteractionCount":29},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What was the main clinical presentation in the case?","Question",{"text":112,"@type":113},"A 77-year-old man presented with abdominal pain and fever.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How was dedifferentiated liposarcoma diagnosed?",{"text":117,"@type":113},"Histopathology showed atypical spindle-cell proliferation, immunohistochemistry was MDM2-positive and CD34/c-kit-negative, and fluorescence in situ hybridization confirmed MDM2 amplification.",{"name":119,"@type":110,"acceptedAnswer":120},"What complication occurred after surgery?",{"text":121,"@type":113},"Six months postoperatively, a penetrating abscess recurred and progressed to an enterocutaneous fistula.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},455207,1791076094,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":29,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":34,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":144,"preview_page_count":4},962090760730,"https://ap-avatar.wpscdn.com/davatar_9964176cb1d06d4a9deccf72a44ae3dc","Clinical Case Reports  \nCASE REPORT  OPEN ACCESS   \nRetroperitoneal Dedifferentiated Liposarcoma With  \nPenetrating Abscess Formation Secondary to Ileal Invasion: A Case Report  \nKenichiro Yambe1 | Kei Nakagawa1  | Kuniharu Yamamoto1 | Hiroto Sakurai1 | Kazuhiro Takami1 | Noriko Kondo1 | Chikashi Shibata2 | Yu Katayose1  \n1Department of Hepato-Biliary-Pancreatic Surgery, Tohoku Medical and Pharmaceutical University Hospital, Sendai, Japan | 2Department of  \nGastrointestinal Surgery, Tohoku Medical and Pharmaceutical University Hospital, Sendai, Japan Correspondence: Kei Nakagawa ([nakagawa.kei@tohoku-mpu.ac.jp](nakagawa.kei@tohoku-mpu.ac.jp))  \nReceived: 3 September 2025 | Revised: 17 November 2025 | Accepted: 20 November 2025  \nKeywords: abscess | dedifferentiated liposarcoma | enterocutaneous fistula | intestinal penetration | MDM2 amplification | retroperitoneal tumor  \nABSTRACT  \nLiposarcoma is a relatively common malignant soft tissue tumor in adults. Dedifferentiated liposarcoma (DLS) is a particularly invasive subtype characterized by high recurrence rates and a poor prognosis. We describe a case ofa retroperitoneal liposarcoma with poor differentiation that presented with peritonitis accompanied by ileal infiltration and perforating abscess formation. A 77-year-old male presented to our hospital with abdominal pain and fever. Computed tomography revealed a 13 cm tumor in the right lower abdomen with internal air density. An ileocecal resection was performed. Histopathological examination revealed a solid proliferation of spindle-shaped atypical cells. Immunohistochemical results were positive for MDM2 and negative for CD34 and c-kit. Fluorescence in situ hybridization confirmed MDM2 amplification, leading to a diagnosis of dedifferentiated liposarcoma. The postoperative course was initially favorable; however, 6 months later, a penetrating abscess recurred and progressed to an enterocutaneous fistula. Intestinal penetration by dedifferentiated liposarcomas is extremely rare. This case highlights the challenges of preoperative diagnosis, the importance of surgical strategies that balance infection control with curative resection, and the need for multidisciplinary management of recurrence.  \n1 | Introduction  \nLiposarcoma accounts for approximately 15%–20% of malignant soft tissue tumors in adults, making it relatively common [1] . According to the World Health Organization, liposarcomascan be categorized into well-differentiated, dedifferentiated, myxoid, pleomorphic, and mixed types [2] . Among these, dedifferentiated liposarcoma (DDLPS) represents 10%–20% of all  \nliposarcomas [3] . DDLPS commonly arises in the retroperitoneum and is characterized by high recurrence rates and local invasiveness, making it a subtype with a poor prognosis [4] .  \nThe incidence of retroperitoneal liposarcoma is reported to be 2.5–2.7 cases per million people, with approximately 30% classified as the dedifferentiated type [5, 6]. Among retroperitoneal tumors, liposarcomas account for approximately 12%–40%[7, 8] .  \n\n| Abbreviations: CDK4, cyclin-dependent kinase 4; CT, computed tomography; DDLPS, dedifferentiated liposarcoma; FISH, fluorescence in situ hybridization; GIST, gastrointestinal stromal tumors; MDM2, mouse double minute 2 homolog; MRI, magnetic resonance imaging; PT, prothrombin time; QOL, quality of life; WDLPS, well-differentiated liposarcoma. |\n| --- |\n| This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.\u003Cbr>© 2026 The Author(s). Clinical Case Reports published by John Wiley & Sons Ltd. |\n\nClinical Case Reports, 2026; 14:e71561 1 of 7  \n[https://doi.org/10.1002/ccr3.71561](https://doi.org/10.1002/ccr3.71561)  \nKey Clinical Message  \nDedifferentiated liposarcomas with intestinal invasion and abscess formation are rare. Preoperative pathological diagnosis remains challenging, re","cbCaiqLJDMKZvV4v","https://ap.wps.com/l/cbCaiqLJDMKZvV4v","pdf",611407,"English","# Introduction\n# Key Clinical Message\n# Case Description and Diagnostic Findings\n## Imaging and Preoperative Challenges\n## Histopathology and Biomarkers (MDM2/CDK4)","[{\"question\":\"What was the main clinical presentation in the case?\",\"answer\":\"A 77-year-old man presented with abdominal pain and fever.\"},{\"question\":\"How was dedifferentiated liposarcoma diagnosed?\",\"answer\":\"Histopathology showed atypical spindle-cell proliferation, immunohistochemistry was MDM2-positive and CD34/c-kit-negative, and fluorescence in situ hybridization confirmed MDM2 amplification.\"},{\"question\":\"What complication occurred after surgery?\",\"answer\":\"Six months postoperatively, a penetrating abscess recurred and progressed to an enterocutaneous fistula.\"}]","Retroperitoneal Dedifferentiated Liposarcoma With Penetrating Abscess Formation Secondary to Ileal Invasion - Case Report | PDF",1790742371,18]