BDNF and polyp: When all100 gallbladder adenocarcinoma, 46 peritumoral, 30 adenoma, 15 polyp and 35 chronic cholecystitis samples were assessed, the positive rate of BDNF was inversely related to that of BMPR1A, due to the analysis of Pearson correlation coefficients (r = −7.482, P < 0.05).