Background <p>Colon cancer located at the splenic flexure exhibits dual lymphatic drainage via the left middle colic artery (lt-MCA) to the superior mesenteric artery (SMA) system and the left colic artery (LCA) to the inferior mesenteric artery (IMA) system. However, an additional pathway—the Arc of Riolan (AoR) artery, central anastomotic vessels connecting the SMA and IMA—may also serve as a route for metastasis. This case highlights the importance of central vascular ligation of the AoR in splenic flexure cancer.</p> Case <p>We present a rare case of isolated AoR lymph node metastasis in a 72-year-old male with advanced splenic flexure cancer. The patient presented with multiple synchronous tumors (splenic flexure, sigmoid, and rectum) and underwent extended left hemicolectomy with central vascular ligation (CVL) of the AoR, revealing metastatic involvement exclusively in AoR nodes. This represents the first documented case of isolated AoR nodal metastasis, emphasizing the need for AoR lymphadenectomy when present.</p> Discussion <p>Recent studies suggest that accessory middle colic arteries (aMCA) and AoR may represent the same anatomical structure, with metastasis rates of 3.7–6.3% in corresponding nodes. Our findings support that AoR should be considered a critical target for CVL in splenic flexure cancer, particularly when identified pre- or intraoperatively.</p> Conclusions <p>Surgeons should recognize AoR as a possible isolated metastatic pathway and perform thorough nodal dissection along this vessel when present to ensure optimal oncologic outcomes.</p>