The distinction of Hodgkin's disease from anaplastic large cell lymphoma.

In this session there seemed to be general agreement on the existence of anaplastic large cell lymphoma (ALCL) as an entity defined by a characteristic morphology and by diffuse expression of the Ki-1 (CD30) antigen. The discussion indicated the lack of specific immunophenotypic and genotypic markers for such a neoplasm and the variability of the clinical patterns associated with it: these include a childhood form, an adult cutaneous form, and an adult nodal disease. While typical cases of ALCL are clearly distinct (by pathologic, cytogenetic, and clinical criteria) from Hodgkin's disease (HD), there is a variety of histologic and immunophenotypic patterns that overlap those of ALCL and HD; most of these would be classified as HD, lymphocyte depletion (LD) or nodular sclerosis (NS), syncytial subtype. No agreed-upon criteria were found that could consistently define these patterns, nor was an agreement possible on whether they are part of a continuum unifying ALCL and HD or phenotypically similar expressions of different diseases.