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

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 wi th 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) transloca tion (or one of its variants). The staining patterns for CD20 and CD79 were typical of diffuse large B-cell lymphoma, CD30 expression was variable, an d most cases (15/22) lacked epithelial membrane antigen (EMA). These findin gs support the view that 'B-cell anaplastic large-cell lymphoma' is unrelat ed to t(2:5)-positive (ALK-positive) lymphoma, and that it represents a mor phological pattern occasionally encountered among diffuse large B-cell lymp homas. By the same reasoning, most tumours diagnosed as ALK-negative anapla stic large-cell lymphoma of T-cell or null phenotype' probably belong to th e spectrum of peripheral T-cell lymphomas.