The current classification of lymphoid neoplasms is based on the integrated utilisation of morphological, immunohistochemical, genetic and clinical criteria to define disease entities. Anaplastic large cell lymphoma is a paradigm for the identification of a disease entity based on morphological observations and immunophenotype, which paved the way for the subsequent discovery of the characteristic cytogenetic abnormality the translocation t(2;5)(p23;q35). In 1994, the t(2;5) was cloned and the NPM-ALK fusion gene generated by this rearrangement was identified. The year 2014 marked the 20^th anniversary of this seminal publication by Steve Morris et al. The discovery of anaplastic lymphoma kinase (ALK) has allowed the definition of a distinct entity within the clinically and pathologically heterogeneous group of CD30+ lymphomas. The diagnosis of ALK-positive ALCL has become straightforward due to the generation of the reliable monoclonal antibody ALK-1 that also has led to the recognition of the histologic spectrum of the disease. ALK-positive ALCL has evolved in the last 20 years to an exciting model for signal transduction studies and targeted therapy.