NTRK1 and bone neoplasm: Mature NGF and proNGF impose distinct macrophage phenotypes through differential engagement of TrkA and p75NTR, with mature NGF enhancing phagocytosis and growth−factor secretion, and proNGF favoring migratory, podosome−rich states; such ligand−form dependence helps explain context−specific myeloid behavior in bone tumors.