报道1例壁外血管侵犯（EMVI）阳性直肠癌患者的诊治经过。患者男，61岁，术前MRI提示cT₃N₁并EMVI阳性，同期CT未见远处转移。2025年7月行直肠癌根治术，术后病理为pT₃N_1b，并见血管侵犯、神经侵犯、肿瘤沉积和高级别肿瘤出芽。因术后乏力、纳差等原因暂缓化疗。9月复查发现肝左叶小结节，遂行肝部分切除并同期还纳回肠造口；术中探查发现脾曲附近腹膜结节并一并切除。病理证实肝病灶及腹膜结节均为结直肠癌转移，分期修订为pT₃N_1bM_1c（ⅣC期）。二代测序显示KRAS p.G13D突变、微卫星稳定（MSS），免疫组化提示错配修复蛋白表达完整（pMMR），随后给予卡培他滨联合奥沙利铂（CAPEOX）方案联合贝伐珠单抗共8周期。2026年5月26日第八周期治疗时复查未见明确进展。本例显示，对于MRI提示EMVI阳性的直肠癌患者，常规CT未见转移并不能完全排除小体积肝转移或低负荷腹膜种植；术中细致探查和分子检测有助于修正分期并安排后续治疗。

This report presents the clinical course of a 61-year-old man with rectal cancer positive for extramural vascular invasion (EMVI). Preoperative MRI suggested cT₃N₁ disease with positive EMVI, while CT did not show distant metastasis. Radical surgery in July 2025 revealed pT₃N_1b disease with vascular invasion, perineural invasion, tumor deposits, and high-grade tumor budding. Chemotherapy was postponed because of postoperative fatigue, poor intake, and reduced performance status. During reassessment in September 2025, a small lesion was found in the left liver. Partial hepatectomy and ileostomy closure were performed, and intraoperative exploration also identified a peritoneal nodule near the splenic flexure. Pathology confirmed colorectal metastases in both lesions, and the stage was revised to pT₃N_1bM_1c. Next-generation sequencing showed KRAS p.G13D mutation and microsatellite stable (MSS) status, and immunohistochemistry indicated proficient mismatch repair (pMMR). The patient subsequently received 8 cycles of capecitabine and oxaliplatin (CAPEOX) plus bevacizumab, with no definite progression on imaging at the eighth cycle on May 26, 2026. This case indicates that negative routine CT findings do not fully exclude small-volume liver or peritoneal metastases in rectal cancer with MRI-detected EMVI. Careful intraoperative exploration and molecular testing may help refine staging and guide subsequent treatment.