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Imaging and combined en bloc resection confirmed high-grade stage IIIb and pT3 pN2b disease, followed by CAPOX adjuvant chemotherapy and multidisciplinary 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cancer.","https://schema.org",{"og:url":32,"og:type":75,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":77,"canonical":32},"index,follow",{"doc_id":79,"site_id":7},456594,1790897359,{"code":4,"msg":82,"data":83},"success",[84,88,92,96,101,106,110,115,119,122,126],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":85,"show_sort_weight":86,"slug":87},"Story & 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1159/000549908\u003Cbr>Received: November 10, 2025\u003Cbr>Accepted: November 25, 2025\u003Cbr>Published online: December 3, 2025 | © 2025 The Author(s) .\u003Cbr>Published by S. Karger AG, Basel [www.karger.com/cro](www.karger.com/cro) |\n\nThis article is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC) ([https://karger.com/Services/OpenAccessLicense](https://karger.com/Services/OpenAccessLicense)). Usage and distribution for commercial purposes requires written permission.  \nCase Report  \nSynchronous Retroperitoneal Pleomorphic Liposarcoma and Colonic MucinousAdenocarcinoma  \nAhmad Al-Bitara Daniel Awada Khaled Sinana Abdullah Tayeba, b Rafat Horouba, b  \na Faculty of Medicine, Damascus University, Damascus, Syrian Arab Republic; bGeneral Surgery Department, Faculty of Medicine, Damascus University, Damascus, Syrian Arab Republic  \nKeywords  \nMultiple primary malignancies · Synchronous neoplasms · Retroperitoneal liposarcoma · Colonic adenocarcinoma · Case report · Adjuvant chemotherapy · CAPOX  \nAbstract  \nIntroduction: Multiple primary malignancies (MPM), defined as two or more distinct primary tumors in 1 patient, are uncommon, with synchronous presentations (diagnosed within 6 months) being rarer. The coexistence of retroperitoneal liposarcoma and a synchronous gastrointestinal malignancy, particularly colorectal adenocarcinoma, is an exceptionally rare clinical entity, posing significant diagnostic and therapeutic challenges. Case Presentation: A 63-year-old male presented with fatigue, anorexia, and weight loss. The initial workup revealed microcytic anemia and positive fecal occult blood. While initial endoscopic biopsies were inconclusive, a contrast-enhanced CT scan identified two distinct masses: a large (20 cm) heterogeneous retroperitoneal mass suggestive of liposarcoma and a thickened right colic flexure. The patient underwent a combined en bloc surgical resection, including an extended right hemicolectomy and resection of the retroperitoneal mass with the right kidney. Histopathology confirmed two high-grade primary malignancies: a retroperitoneal pleomorphic liposarcoma (stage IIIb) and acolonic mucinous adenocarcinoma (stage pT3 pN2b) . Adjuvant chemotherapy (CAPOX regimen) was initiated for high-risk colon cancer. Conclusion: This case highlights the necessity of a high index of suspicion for synchronous malignancies in patients with nonspecific constitutional symptoms. Comprehensive cross-sectional imaging is crucial for accurate staging. Management requires a multidisciplinary approach to plan complex  \nCorrespondence to:  \nAhmad Al-Bitar, [dr.ahmad.al.bitar](dr.ahmad.al.bitar)  gmail.com  \nCase Reports in Oncology  \nCase Rep Oncol 2026;19:52–66 53  \n\n| DOI: 10. 1159/000549908 | © 2025 The Author(s) . Published by S. Karger AG, Basel [www.karger.com/cro](www.karger.com/cro) |\n| --- | --- |\n\nAl-Bitar et al.: Synchronous RPLS and Colonic Mucinous Adenocarcinoma  \nsurgical interventions and tailor adjuvant therapy, often prioritizing the more aggressive or higher stage malignancy. This report underscores the complexity of MPM and the need for individualized patient care.  \n© 2025 The Author(s) .  \nPublished by S. KargerAG, Basel  \nIntroduction  \nMultiple primary malignancies (MPM) are defined as the occurrence of two or more independent primary malignant tumors in the same patient, each histologically distinct and none representing a metastasis of another [1–3] . They are classified as synchronous or metachronous. According to the International Agency for Research on Cancer (IARC) and the International Association of Cancer Registries (IACR), synchronous tumors are defined as those diagnosed within 6 months of each other, whereas metachronous tumors occur after 6 months [4]. Globally, the reported incidence of MPM varies widely, affecting approximately 2–17% of cancer patients [1] . Synchronou","cbCaib04bSz4XraF","https://ap.wps.com/l/cbCaib04bSz4XraF","pdf",5092927,15,"English","# Introduction\n## Multiple primary malignancies and synchronous criteria\n## Retroperitoneal liposarcoma overview\n## Colorectal cancer in MPM\n\n# Case Presentation\n## Clinical symptoms and history\n## Laboratory and endoscopic findings\n## Imaging and surgical management\n## Histopathology and staging\n## Adjuvant chemotherapy and follow-up\n\n# Conclusion","[{\"question\":\"What defines synchronous multiple primary malignancies in this report?\",\"answer\":\"Synchronous tumors are diagnosed within 6 months of each other and represent independent primary malignancies rather than metastases.\"},{\"question\":\"What diagnostic process led to identifying both tumors?\",\"answer\":\"After inconclusive initial endoscopic biopsies, contrast-enhanced CT revealed two distinct masses, and combined en bloc surgical resection confirmed the diagnoses histopathologically.\"},{\"question\":\"How was treatment planned and delivered for the patient?\",\"answer\":\"The patient underwent extended right hemicolectomy and resection of the retroperitoneal mass with the right kidney, followed by CAPOX adjuvant chemotherapy for high-risk colon cancer.\"}]","Synchronous Retroperitoneal Pleomorphic Liposarcoma and Colonic Mucinous Adenocarcinoma | PDF",1790746470,38]