BDNF and neoplasm: Additionally, serum BDNF concentrations declined significantly after the operations in patients with (TNM stage IV) and without (TNM stages I, II, and III) distant metastases; in patients with angioinvasions (preoperative: 25.425 ng/ml, SD = 9.489 vs. postoperative: 21.203 ng/ml, SD = 8.199, p = 0.0505), in those without neuroinvasions (preoperative: 27.108 ng/ml, SD = 8.201 vs. postoperative: 23.911 ng/ml, SD = 9.032, p = 0.049713), and in those with tumours below the median size (preoperative: 27.749 ng/ml, SD = 9.287 vs. postoperative: 21.337 ng/ml, SD = 7.843, p = 0.0187).