Primary Ki-1-positive anaplastic large-cell lymphoma: A distinct clinicopathologic entity

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Abstract
The morphology of anaplastic large-cell lymphoma (ALCL) is associated with a clinical syndrome of peripheral lymphadenopathy (>80%) and frequent extranodal disease (>40%) in children and young adults (median age + , CD45 + , CD15 − , EMA + , BNH9 + , keratin − , lysozyme − ). A recurrent cytogenetic translocation, t(2; 5) (p23; q35), has been observed among morphologic variants, including a small-cell-predominant variant and tumor cell line which contains a spectrum of small cerebriform and large anaplastic CD30 + cells. 70% of ALCL cases are of T-cell lineage, 15% B, 5% T/B, and 10% undefined. ALCL appears to be distinct from peripheral T-cell lymphomas such as HTLV-1 + adult T-cell leukemia, angioimmunoblastic lymphadenopathy, angiocentric T-cell lymphoma, and mycosis fungoides, which occur mainly in older patients. These combined clinical, pathologic, immunophenotypic, and cytogenetic observations support the concept that ALCL is a distinct clinicopathologic entity.