Supplementary Material for: Small duodenal adenocarcinoma with peritoneal dissemination mimicking duodenal Brunner’s gland hyperplasia

Abstract Introduction: Gastric-phenotype non-ampullary duodenal carcinomas are rare but potentially aggressive tumors. Case Presentation: A 52-year-old woman was referred for a duodenal polyp. Endoscopy revealed multiple duodenal bulb polyps suggestive of Brunner’s gland hyperplasia. Histopathology confirmed well-differentiated tubular adenocarcinoma with submucosal invasion and a positive margin. The patient underwent pancreaticoduodenectomy, and residual subserosal carcinoma was detected. Despite adjuvant chemotherapy, liver metastases and peritoneal dissemination developed 7 months postoperatively. The patient died 24 months after surgery. Conclusion: This case highlights the aggressive nature of gastric-phenotype duodenal adenocarcinoma and the need for early radical surgical intervention when vertical margins are positive after endoscopic resection.摘要 引言：胃表型非壶腹十二指肠癌是一类罕见但具有潜在侵袭性的肿瘤。病例报告：一名52岁女性因十二指肠息肉转诊。内镜检查可见十二指肠球部多发息肉，提示为布伦纳腺增生（Brunner’s gland hyperplasia）。组织病理学证实为高分化管状腺癌，伴黏膜下层浸润，且切缘阳性。患者接受胰十二指肠切除术，术后检出浆膜下残留癌灶。尽管予以辅助化疗，术后7个月仍出现肝转移及腹膜播散。患者于术后24个月死亡。结论：本病例凸显了胃表型十二指肠腺癌的侵袭性特征，以及内镜切除后若垂直切缘阳性，则需尽早开展根治性手术干预的必要性。