Although the field of neoplastic haematopathology has never been at a loss for terminological controversy, the entity that until further notice is identified as “anaplastic large cell lymphoma” (ALCL), has provoked an exceptionally persistent confusion of tongues.

In 1985, Stein et al initiated the history of ALCL by isolating a group of tumours “comprised solely of cells showing both morphological (anaplastic features) and immunological (CD30 immunoreactivity) similarities to the neoplastic cells in Hodgkin's disease” in the lymphoma category Rappaport would have indicated as “diffuse histiocytic lymphoma”.¹ Because the diagnosis “Ki-1 positive large cell lymphoma” could be established quite reproducibly, and because this malignancy seemed to feature distinctive morphological, immunophenotypical, genotypical, and clinical properties, ALCL of T or null cell phenotype was ultimately recognised by the members of the international lymphoma study group and incorporated in the REAL classification as a separate entity.²

However, with regard to none of the four fundamental aspects characterising a given malignancy do ALCLs appear a homogeneous collection.

By pure morphology, at least seven different …