BDNF expression was significantly lower in well-differentiated adenocarcinomas with maximum tumor diameter <2 cm, no metastasis to lymph nodes, and no invasion of regional tissues compared to poorly-differentiated adenocarcinomas with maximal tumor diameter >2 cm, metastasis of lymph node, and invasiveness of regional tissues in gallbladder adenocarcinoma. The gene discussed is BDNF; the disease is neoplasm.