ALK(+) ALCL by definition overexpresses an ALK fusion gene, typically t(2;5)(q23;35) (80% of cases) which fuses the 3′-part of the ALK (Anaplastic Lymphoma Kinase) gene on chromosome 2p23 with the 5′-part of the nucleophosmin (NPM1) gene on chromosome 5q35, resulting in an NPM-ALK chimeric protein with constitutive tyrosine kinase activity [36]. This evidence concerns the gene NPM1 and anaplastic large cell lymphoma.