ALK and anaplastic large cell lymphoma: Among them, anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) represents a biologically distinct subtype driven by constitutive activation of ALK fusion proteins, which promote oncogenic signalling through signal transducer and activator of transcription 3, phosphatidylinositol 3-kinase (PI3K)/AKT Serine/Threonine Kinase 1 (AKT)/mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase pathways.