PubMed1998
In 1994 the International Lymphoma Study Group (ILSG) published the "Revised European-American Classification of Lymphoid Neoplasms" (R.E.A.L. Classification). Lymphomas were classified according to their presumed normal counterparts, to the extent possible. Within both T- and B-cell categories differentiation between lymphomas and/or leukemias of "precursor" or "peripheral" neoplasms are defined arising from antigen independend or antigen reactive cell proliferation. Lymphomas undoubtedly characterized by currently available morphologic, immunologic, and genetic technics represent "real" disease entities. Provisional categories include lymphomas that have been described in some detail, but without consensus within the ILSG. Proposed names are based predominantly on established usage. With respect to similar treatment approaches and difficulties of the ILSG members in subclassifying large cell lymphomas, centroblastic, immunoblastic and large cell anaplastic lymphomas of B-cell type were "lumped" together as large B-cell lymphomas. Within a prospective treatment trial overall survival was significantly better in centroblastic as compared to B-cell immunoblastic lymphoma diagnosed by optimal histomorphology according the criteria of the Kiel Classification. Thus the R.E.A.L. Classification fails to identify patients who may require other than standard treatment. Future studies will demonstrate whether subclassifying the proposed "peripheral" T-cell lymphomas, unspecified into T-zone lymphoma, lymphoepitheloid (Lennert's) lymphoma and pleomorphic, small, medium, and large cell lymphomas according the Kiel Classification is of clinicopathologic relevance. On the contrary the subtypes of chronic lymphocytic leukemia of T-cell type form two distinct entities within the R.E.A.L. Classification separating T-CLL/prolymphocytic leukemia from large granular lymphocyte leukemia of T- and NK-cell type. Within the R.E.A.L. Classification the lymphoplasmacytoid immunocytoma of the Kiel Classification will be subsumed together with the prognostically significantly better B-cell chronic lymphocytic leukemia. Opposite to the original intention of the ILSG two proposals are developed on clinical grouping of entities. Clinical indolent lymphoid neoplasms usually have "low grade" histologic appearances, with a predominance of small cells subsuming with the exception of the mantle cell lymphoma all of the low grade lymphomas of the Kiel classification. Aggressive lymphomas (intermediate risk) are defined as tumors whose survival if untreated is measured in months, highly or very aggressive lymphomas and/or leukemias will kill untreated patients within weeks. Unlike the Kiel Classification proposed categories subsume lymphomas irrespective of cytomorphology, thus grouping together potentially curable and uncurable diseases. Undoubtedly the R.E.A.L. Classification forms at present the best compilation of existing knowledge upon neoplasms of the immune system, enabling cooperation between clinicians and scientists all over the world. According to the ILSG this proposal should be considered a starting point for future periodic reevaluations.