Dlbcl And Burkittlike Lymphoma

The classification of large B-cell lymphomas as a single group has been controversial. Various morphologic subtypes have been recognized including centroblas-tic, immunoblastic, anaplastic, and T-cell rich but the clinical significance of subclassifying DLBCL in this way is of doubtful significance and they do not appear to constitute separate diseases. There are, however, three rare large B-cell lymphomas that do appear to merit the designation as distinct diseases namely primary mediastinal (thymic) large B-cell lymphoma,33 intravascular lymphoma,34 and primary effusion lymphoma.35 There is little doubt that within the category of DLBCL there are at least several more distinct entities that might benefit from different therapies. Their recognition is one of the challenges faced by hematopathologists, and gene profiling techniques have already shown great promise in this area. The original study using this technique25 showed that it was possible to recognize two major clinically significant groups of DLBCL, those derived, respectively, from germinal center cells and so-called activated B cells. Subsequently, a third group has been recog-nized36 and a further study has vindicated the separate classification of mediastinal large B-cell lymphoma.37

The borderline between DLBCL and BL is not always clear-cut. The WHO clinical advisory meeting took the decision that those DLBCL with Burkitt-like morphology that did not strictly conform to that of BL, but with c-myc rearrangement and a proliferation fraction of 100%, are best termed "atypical BL" and should receive therapy tailored for BL. Thus, they represent a subtype of BL, the others being endemic BL, nonen-demic BL, and immunodeficiency-associated BL.

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