ALK (Anaplastic Lymphoma Kinase) is a member of the receptor tyrosine kinase family, primarily composed of an extracellular ligand-binding domain, a single transmembrane domain, and an intracellular tyrosine kinase domain. ALK is expressed during embryonic development and at lower levels in adult tissues, predominantly localized in limited tissues such as the brain and lungs, participating in neurodevelopment, proliferation, and survival. By binding with ligands such as MID1, ALK activates downstream signaling pathways like RAS/MAPK, PI3K/AKT, and JAK/STAT, influencing cell fate. Its specific expression is in the nervous system, and gene rearrangements, mutations, or overexpression are common in cancers such as non-small cell lung cancer, lymphoma, closely associated with tumorigenesis and progression.