报道1例胃原发未分化肉瘤的罕见病例，分享其诊断、鉴别经验，总结其治疗、挑战、临床经验、组织病理学特征和相关文献综述。患者老年男性，既往2型糖尿病史，反复黑便史5年余。2024年7月因再次出现黑便入院，检查提示重度贫血，胃镜检查发现胃窦后壁4.0 cm×4.0 cm不规则增生，活检病理结果为溃疡坏死伴肉芽组织形成，并伴轻度不典型增生。CT提示肿瘤大小7 cm×3 cm×2.6 cm，侵及胃壁全层。患者接受胃部分切除治疗，术中完整切除肿瘤及周围组织，未见肿大淋巴结。术后病理结果显示胃高级别未分化肉瘤，肿瘤侵犯胃壁全层，未见脉管内瘤栓及淋巴结转移。术后恢复顺利，已行多柔比星＋异环磷酰胺＋美司钠(AIM)方案化疗6次，至今无复发迹象，目前正密切随访。该病例展示了胃肉瘤的诊断与治疗过程，强调了及时、全面的诊断检查对于正确诊断和治疗方案选择的重要性。胃未分化肉瘤属于较罕见病理分型，缺乏特异性临床表现，引起的反复发作性消化道出血，容易与其他胃部恶性肿瘤混淆，因此在临床中应高度重视胃镜及其他影像学检查。手术切除仍然是主要治疗方式，而术后辅助治疗、随访对于预防复发和提高生存率至关重要。

Presents a case of primary gastric undifferentiated sarcoma, where the patient, an elderly male with a history of type 2 diabetes and recurrent melena, was admitted with severe anemia. Gastroscopy revealed a 4 cm×4 cm irregular mass in the gastric antrum, and biopsy indicated ulceration, necrosis, and mild atypical hyperplasia. CT scans showed a 7 cm×3 cm×2.6 cm tumor involving the full thickness of the gastric wall. The patient underwent partial gastrectomy, and postoperative pathology confirmed high-grade undifferentiated sarcoma without lymph node metastasis. Recovery was smooth, and follow-up is ongoing. This case underscores the importance of thorough diagnostics and highlights surgery as the primary treatment, with close postoperative monitoring to prevent recurrence.