CEACAM5 and gallbladder cancer: GBC: gallbladder cancer; TLC: total leucocyte count; ALP: alkaline phosphatase; CEA: carcinoma embryonic antigen; CA 19-9: carbohydrate antigen 19-9; CD: Clavien-Dindo; EUS: endoscopic ultrasonography; FNAC: fine-needle aspiration cytology; AST: aspartate aminotransferase; ALT: alanine aminotransferase; ECOG: Eastern Cooperative Oncology Group; IGBC: incidental gallbladder cancer; CDC: choledochal cyst; PTBD: percutaneous transhepatic biliary drainage