The appropriate surgical treatment was investigated for T1b gallbladder (GB) cancer through a retrospective analysis of the clinical outcomes of patients with incidental T1 GB cancer. Methods

Patients with T1 GB cancer who were incidentally diagnosed while undergoing a simple cholecystectomy at Chungnam University Hospital from January 2004 to December 2017 were enrolled. Overall, 39 patients with T1 GB cancer, 17 patients with T1a, and 22 patients with T1b were included. We retrospectively analyzed the patients' clinical and pathologic findings and follow-up results. Results

Among the 6490 patients who underwent cholecystectomy during the study period, 165 patients were diagnosed with GB cancer (T1=42 [25.5%]). The risk factor associated with recurrence and cancer-related death in patients with T1 GB cancer was lymphovascular invasion (recurrence, p =0.028; death, p =0.004). In the T1b group, the 5-year disease-free survival (DFS) rate showed a statistical difference between patients with and without lymphovascular invasion (45.7% vs. 83.6%, p =0.048). There was no statistically significant difference in 5-year DFS and overall survival rate between simple cholecystectomy and extended cholecystectomy in T1b GB cancer with lymphovasular invasion ( p =0.054 and p =0.091, respectively). Conclusions

In incidental T1b GB cancer, extended cholecystectomy was not superior to simple cholecystectomy in terms of the 5-year DFS rate and nor in overall survival rate or recurrence rate, even when lymphovascular invasion was identified after simple cholecystectomy. Therefore, simple cholecystectomy may be recommended as a primary surgical strategy for T1b GB cancer.