BACKGROUND: T4 hepatocellular carcinoma(HCC) with invasion to adjacent structure(s) may require resection of not only the tumor but also the invaded structure(s). This study aims to assess whether such combined resection for T4 HCC is justifiable.METHODS: Adult patients with T4 HCC were divided into three groups. Group 1: tumors and invaded adjacent structures were resected together if histopathologically confirmed tumor invasion; group 2: same as group 1 but histopathologically confirmed tumor adhesion; group 3: tumor resection only. Group comparisons were made.RESULTS: Totally 144 patients were included in the study.There were 71, 14 and 59 patients in groups 1, 2 and 3, respectively. The groups were comparable in demographics, complication and survival. Ten hospital deaths occurred(5, 0 and 5 in groups 1, 2 and 3, respectively; P=0.533). The 5-year overall survival(hospital mortality excluded) was 17.8% in group 1,14.3% in group 2, and 28.9% in group 3(P=0.191). The 5-year disease-free survival was 10.4% in group 1 and 14.5% in group 3(no data for group 2 yet)(P=0.565). On multivariate analysis,macrovascular invasion and poor differentiation were risk factors for survival whereas combined resection did not impact patients’ survival. CONCLUSIONS: Combined resection achieved survival outcomes similar to tumor resection only. Patients with tumor invasion and those with tumor adhesion had comparable survival after combined resection. At centers with the required expertise, combined resection should be attempted to treat T4 HCCs with clinically suspected invasion of adjacent structures. BACKGROUND: T4 hepatocellular carcinoma (HCC) with invasion to adjacent structures (s) may require resection of not only the tumor but also the invaded structure (s). This study aims to assess whether such combined resection for T4 HCC is justifiable. METHODS: Group 1: tumors and invaded adjacent structures were resected together if histopathologically confirmed tumor invasion; group 2: same as group 1 but histopathologically confirmed tumor adhesion; group 3: tumor resection only. Group comparisons Tested were 144 patients were included in the study. There were 71, 14 and 59 patients in groups 1, 2 and 3, respectively. The groups were comparable in demographics, complication and survival. Ten hospital deaths occurred (5, The 5-year overall survival (hospital mortality excluded) was 17.8% in group 1, 14.3% in group 2, and 28.9% in group 3 (P and 0.5 in groups 1, 2 and 3, respectively; P = 0.533) = 0.191). The 5-year disease-f ree survival was 10.4% in group 1 and 14.5% in group 3 (no data for group 2 yet) (P = 0.565). On multivariate analysis, macrovascular invasion and poor differentiation were risk factors for survival but combined resection did not impact patients’ survival of patients with tumor invasion and those with tumor adhesion had comparable survival after combined resection. At centers with the required expertise, combined resection should be attempted to treat T4 HCCs with clinically suspected disease invasion of adjacent structures.