BDNF and head and neck squamous cell carcinoma: Using RNA isolation, reverse transcription, PCR, and in situ hybridization, the mRNA expression of BDNF and NTRK2, and using immunohistochemistry, the protein synthesis of the NTRK2 gene product TrkB were investigated in normal mucosa from uvulopalatopharyngoplasties (UPPP) and in HNSCC tumor tissue.