{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T05:18:39Z","timestamp":1787635119755,"version":"build-2736575974"},"reference-count":25,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T00:00:00Z","timestamp":1787616000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Med."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Early-onset colorectal cancer (EO-CRC) is often characterized by a highly aggressive nature and insidious onset. Herein, we report a rare case of fulminant, early-onset colon cancer presenting with a massive pelvic seeding metastasis driven by concurrent KRAS and TP53 mutations. This study aims to elucidate the molecular mechanisms underlying its hyper-progressive course and provide critical insights into clinical differential diagnosis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case description<\/jats:title>\n                    <jats:p>A 44-year-old female presented with intermittent abdominal pain for 8\u202fmonths, which worsened alongside abdominal distension for 10\u202fdays prior to admission. Notably, an abdominopelvic CT scan performed 8\u202fmonths earlier had yielded unremarkable findings. Upon admission, laboratory evaluations revealed a fulminant elevation of serum tumor markers (CEA: 256.63\u202fng\/mL, CA19-9: 3,724.63\u202fU\/mL), and an abdominopelvic CT, subsequently confirmed intraoperatively, revealed a massive (~20\u202fcm) cystic-solid pelvic mass accompanied by 1,000\u202fmL of ascites. The primary lesion was identified as a 3.1\u202fcm sigmoid colon adenocarcinoma. The patient successfully underwent combined radical resection. Postoperative histopathology confirmed that the pelvic mass was a metastasis originating from the colon adenocarcinoma [CDX2 (+), CK20 (+)], exhibiting lymphovascular invasion and intermediate tumor budding (Grade Bd2). Next-generation sequencing (NGS) demonstrated that the tumor was microsatellite stable (MSS) and harbored concurrent pathogenic mutations in KRAS (p.G12D, 28.70%) and TP53 (p.I195T, 42.50%), conferring intrinsic resistance to conventional anti-EGFR monoclonal antibodies and immunotherapy. Consequently, a multidisciplinary team (MDT) formulated a therapeutic strategy consisting of systemic adjuvant chemotherapy with bevacizumab plus mFOLFOX6, paired with high-frequency follow-up.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Early-onset MSS colorectal cancer, driven by concurrent KRAS\/TP53 mutations, can exhibit extreme, hyper-progressive malignant behavior. A recent negative screening result cannot entirely rule out the development of interval colorectal cancer. Clinicians must maintain a high index of suspicion for primary gastrointestinal malignancies when encountering massive cystic-solid pelvic masses in female patients. Timely multi-gene NGS panel testing is crucial to deciphering multi-drug resistant oncogenic driver axes and tailoring individualized precise treatment strategies.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fmed.2026.1900343","type":"journal-article","created":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T04:23:06Z","timestamp":1787631786000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Fulminant development of a giant pelvic metastasis from microsatellite-stable early-onset sigmoid colon cancer with KRAS and TP53 co-mutations: a case report"],"prefix":"10.3389","volume":"13","author":[{"given":"Shouxin","family":"Wei","sequence":"first","affiliation":[{"name":"Department of Gastrointestinal Surgery, Suining Central Hospital","place":["Suining, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sijia","family":"Yu","sequence":"additional","affiliation":[{"name":"Department of General Practice, Suining Central Hospital","place":["Suining, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yunsheng","family":"Lan","sequence":"additional","affiliation":[{"name":"Department of Gastrointestinal Surgery, Suining Central Hospital","place":["Suining, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,8,25]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"25560","DOI":"10.1073\/pnas.1912772117","article-title":"Driver mutations of the adenoma-carcinoma sequence govern the intestinal epithelial global translational capacity","volume":"117","author":"Smit","year":"2020","journal-title":"Proc Natl Acad Sci 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