Abstract:Primary liver cancer is a highly malignant hepatic tumor with a low early diagnosis rate and poor prognosis, and hepatectomy remains the primary curative treatment. However, massive liver cancer patients often lose surgical opportunities due to insufficient future liver remnant volume and major vascular invasion. The traditional static Couinaud liver segmentation fails to explain intraoperative hepatic hemodynamic changes and tissue compensation, while the dynamic hepatic blood flow watershed theory provides novel theoretical support for complex liver cancer surgical planning. This study reported a 34-year-old male with post-hepatitis B cirrhosis and massive primary liver cancer stage Ⅲa, who presented with right upper abdominal pain after trauma, accompanied by significant weight loss and elevated liver function indexes and tumor markers. Imaging showed a large right hepatic tumor invading the right hepatic vein. Preoperative three-dimensional visualization and multi-disciplinary team evaluation recommended neoadjuvant conversion therapy followed by surgery, which was declined by the patient. Extended hepatectomy was successfully performed under the guidance of the dynamic hepatic blood flow watershed theory, with postoperative pathology confirming moderately differentiated hepatocellular carcinoma. The patient recovered uneventfully, receiving antiviral therapy, targeted immunotherapy combined with transcatheter arterial chemoembolization （TACE）.Subsequent sacral and pulmonary metastases occurred, and second-line targeted immunotherapy was initiated. The patient eventually died of extensive systemic metastasis and multiple organ failure at 15 months after surgery. This case confirms that the dynamic hepatic blood flow watershed theory can expand the indications of extended hepatectomy for giant liver cancer and ensure surgical safety. Nevertheless, for advanced giant liver cancer complicated with major vascular invasion, direct surgery alone yields limited long-term efficacy. Individualized neoadjuvant or down staging conversion therapy followed by sequential surgery is clinically recommended to improve the R0 resection rate, reduce early recurrence, and optimize patients’ quality of life and long-term prognosis.