Mediastinal B-cell lymphoma: A study of its histomorphologic spectrum based on 109 cases

Mediastinal B-cell lymphoma (MBL) is a distinct variant of aggressive non-H odgkin's lymphoma with characteristic clinical and biological features but less well-defined histomorphology. We reevaluated 124 biopsy specimens from 109 MBL patients of an Italian/ French/German retrospective clinical study . MBL was primarily diagnosed on clinical and histological grounds in conju nction with the detection of CD20 expression by immunohistology. Cytologica lly, MBL features limited intralesional but considerable interindividual cy tological diversity, ranging from medium-sized to very large, atypical cell s. Sclerosis and necrosis are restricted to extrathymic and extranodal site s of involvement, predominantly the lung, as is angioinvasion,which predomi nantly affects larger vessels. The medium-sized and the large cell variants resemble marginal zone lymphoma variants, whereas the very large cell vari ant of MBL has not so far been found to have any extramediastinal counterpa rt. We conclude that MBL displays a broad morphological spectrum covering m ore than is implied by the term "diffuse large cell lymphoma." Because stat istical analysis of cytological and histological criteria failed to correla te with prognosis in this comprehensive group of patients, we think it inad visable further to subclassify MEL. HUM PATHOL 90:178-187. Copyright (C) 19 99 by W.B. Saunders Company.