A practical approach to the pathology of lymphoid neoplasms: a revised European-American classification from the International Lymphoma Study Group.

This formulation includes a number of disease entities which may alarm those who believe that a lymphoma classification must be simple. The fact remains that these are the tumors that pathologists are seeing and diagnosing, and oncologists must be prepared to deal with them. If several morphologically, immunologically and genetically distinct neoplasms prove to respond identically to currently available treatment, the can be "lumped" for the purposes of clinical treatment selection (see Table 11-3). However, if new forms of treatment become available, particularly if these are directed against antigenic or genetic features, it will be important to recognize and study each disease separately. This study should be regarded as a preliminary effort to develop a consensus on lymphoma categorization, and constitutes merely a framework for further study. The ILSG has not attempted to determine the reproducibility of diagnosis of the various categories, either among different pathologists or by the same pathologist over time. No prior tumor classification has been based on reproducibility and when such studies have been done with existing classifications of lymphoma, they have shown disappointing results. 1,35,119 It is likely that recognition of clearly defined entities, which have characteristic immunophenotypes and in some cases genetic features, as well a characteristics morphology, will facilitate reproducibility among pathologists.189 Formal reproducibility studies should be undertaken, and should in general be a more frequent activity in the pathologic diagnosis of tumors. The ILSG does not have the resources to make a systematic attempt to determine the utility of these histologically and immunologically defined categories in predicting clinical outcome. The task of the pathologist is to attempt to define diseases by morphologic and other criteria applied to tissue specimens, and this has been the goal of the current endeavor. The clinical information about the different entities is taken from studies already published, which clearly show that each of the entities has distinctive clinical behavior, even if distinctive treatments are not currently available. The joint task of clinical oncologist and hematopathologists now is to undertake systematic application of the criteria presented here to defined groups of patients, to determine whether the newly-recognized categories will help to further stratify treatment response and outcome in clinical trials. Several members of the ILSG have already begun to review cases in cooperative group trials, and have found the recognition of these entities within broad Working Formulation categories can have prognostic implications (Grogan, T and Banks, PM, unpublished data from the Southwest Oncology Group [SWOG]).(ABSTRACT TRUNCATED AT 400 WORDS)