Anaplastic large‐cell lymphomas of B‐cell phenotype are anaplastic lymphoma kinase (ALK) negative and belong to the spectrum of diffuse large B‐cell lymphomas

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Abstract
There is controversy in the literature as to whether anaplastic large‐cell lymphoma of B‐cell phenotype is related to the t(2;5)‐positive T‐ or ‘null’ cell lymphoma of the same morphology. We report a study of 24 lymphomas with morphological features of anaplastic large‐cell lymphoma which expressed one or more B‐cell markers and lacked T‐lineage markers. Clinical features were more in keeping with large B‐cell lymphoma than with classical t(2;5)‐positive anaplastic large‐cell lymphoma, and immunostaining for anaplastic lymphoma kinase (ALK) protein provided no evidence for the (2;5) translocation (or one of its variants). The staining patterns for CD20 and CD79 were typical of diffuse large B‐cell lymphoma, CD30 expression was variable, and most cases (15/22) lacked epithelial membrane antigen (EMA). These findings support the view that ‘B‐cell anaplastic large‐cell lymphoma’ is unrelated to t(2;5)‐positive (ALK‐positive) lymphoma, and that it represents a morphological pattern occasionally encountered among diffuse large B‐cell lymphomas. By the same reasoning, most tumours diagnosed as ‘ALK‐negative anaplastic large‐cell lymphoma of T‐cell or null phenotype’ probably belong to the spectrum of peripheral T‐cell lymphomas.