GCG and neoplasm: Analysis of the physiological characteristics of many biologically active substances produced by the Diffuse Neuro-Endocrine System (DNES) [110], such as melatonin, serotonin, gastrin, insulin, glucagon, somatostatin, etc., confirms the important role of the hormones of these cells in the stages of tumor onset and proliferation, while the decrease in the number of these cells in the terminal stages of the tumor is significant [111].