The proposal for a Revised European American Lymphoma classification—a new start of a transatlantic discussion

The Editorial Board invited me to give a balanced assessment of the proposed Revised European American Lymphoma classification, known as the REAL classification, perhaps presenting views which are in disagreement with the proposed classification. This I shall try to do as best I can, though not without certain misgivings. Actually, I had not intended to comment on the proposed REAL classification, because I thought I had spent enough years working towards an optimum classification and arguing its merits. I felt the time had come to pass the baton on to the next generation and let younger people develop their own ideas. However, it appears that people really are waiting for my opinion. The objective of the authors of the proposed classification is ‘an international consensus on terminology, in the hope of improving communication among pathologists and clinicians’. This is a noble goal, and it outweighs more than certain reservations we might utter. The publication by Chan et a1.l includes a table comparing the REAL classification with the updated Kiel classification, which makes ‘it clear, in all fairness, that it is essentially a modified Kiel classification. Should this not please me? Since I was asked, I should also point out those aspects that bother me. Some of them are related more to the principles of a classification, others apply to details. The term REAL classification is misleading in several ways. The reader will at any rate ask himself which classification was revised. In the words of Chan et aL1, the new classification is supposed to be ‘simply a list of well-defined, biological entities’. In other words, it is not actually a classification. Accordingly, no conceptual basis is recognizable that would make it easier to understand the many entities better and make it easier to learn and teach the REAL classification. The REAL classification is, thus, a pragmatic, not purely scientific approach to presenting the various entities of malignant lymphoma. In its compilation, compromises were evidently necessary. Compromises are useful in politics, but they are inappropriate in science, which strives after truth rather than a consensus. The consensus will come about of its own accord once objectifiable data exist. We should not insist on quibbling about semantics or terminology, however. Here, a willingness to compromise is appropriate, as long as proven facts and biological laws are not being thrown overboard. I am aware that a subdivision into low and high grade lymphomas-perhaps one could find more appropriate synonyms-is a simplification and has its drawbacks. Nevertheless, a classification should contain this subdivision, making it clear that virtually every low grade lymphoma can transform into a high grade type and that the result is not merely a variant of the low grade type, but that there is a quantum leap between the two. Such a secondary high grade lymphoma corresponds to the blast crisis in chronic myeloid leukaemia. Understanding this is important for the clinician. He must realize whether a given case is one of primary or secondary high grade (blasticl) lymphoma, because clinical studies have shown that secondary high grade lymphomas have a much worse prognosis than primary high grade lymphomas of the same cell type. The REAL classification comprises nodal and extranodal lymphomas-in contrast to the published table of the updated Kiel classification (the only exception: cerebriform lymphocytic lymphoma). Most of the extranodal lymphomas are described in ‘addenda’. This will do, if one is content to simply have a list of lymphoma types, but it may have its disadvantages. Depending on the organ or organ system, extranodal lymphomas show specific peculiarities that are swept under the carpet in such a list of lymphomas, unless we extend the list ad infinitum. Examples of organ or organ/ system-specific lymphomas are well known in the MALT system, the skin, the brain, the spleen, the blood vessels and others. No wonder that the stimulating monograph by Isaacson and Norton2 on extranodal lymphomas is of similar length to our description of the nodal lymphomas3. Yet its authors are in agreement that this is just the beginning and that there is no telling what its ultimate scope will be, or where and when it will end. A new classification should be based on confirmed entities. Provisional entities should first be substantiated