Comparative pathologic features of genetic subtypes of ALCL. (A) Percentage of cases with unanimous consensus on a diagnosis of ALCL, based on morphology, phenotype, and clinical data. (B) Percentage of cases with unanimous consensus on the presence of classic histologic features of ALCL, as assessed without knowledge of phenotype (except CD30 expression) or clinical data. (C) Immunophenotypic markers that differed significantly among genetic subtypes. As a defining feature of ALK-positive ALCL, immunohistochemistry for ALK is not included here.