NGF and neoplasm: The tumor cells release a multitude of cytokines and mediators that recruit and activate inflammatory cells (T-cells, mast cells, macrophage, stromal cells); disrupt the equilibrium of osteoclasts (receptor activator of nuclear factor kappa-Β ligand (RANKL)) and osteoblasts (endothelin (ET)); and activate the nociceptive fibers of the sensory nervous system (prostaglandin E2 (PGE2), adenosine triphosphate (ATP), lactic acid and H+, ET, tumor necrosis factor (TNF) alfa, interleukin (IL) 6, -8, -15,-16, NGF, bradykinin, ...), causing the pain sensation.