BDNF and gallbladder adenocarcinoma: BDNF expression was significantly lower (P < 0.05) and BMPR1A was significantly higher (P < 0.05) in the well-differentiated gallbladder adenocarcinomas with maximum diameter of <20 mm, no metastasis to lymph nodes, and no invasion of regional tissues, compared with poorly differentiated tissues with maximal mass diameter of >20 mm, metastasis to lymph nodes, and invasion of regional tissues.