Marginal-zone B-cell lymphoma, extranodal-malt-type: Report of three cases

A high proportion of extranodal lymphoid infiltrates are diffuse small lymp hocytic proliferations [1, 2] and therefore pose a particularly challenging diagnostic problem [1-4]. Their benign or malignant nature cannot be deter mined using clinical and radiologic criteria. The application of traditiona l morphologic criteria (i.e., cytologic maturity and polymorphism favor ben ignancy while cytologic atypia and monomorphism favor malignancy) [5, 6], h as probably improved diagnostic accuracy. However. these criteria generally have not been helpful in evaluating the large number of lymphoid infiltrat es composed of monomorphic collections of small cytologically-mature appear ing lymphoid cells [1-4] and, therefore, have not always accurately predict ed clinical behavior. Extranodal lymphoid proliferations are also of considerable biologic intere st since their pathogenesis and natural history have not . been fully eluci dated Localized non-Hodgkin's lymphoma, extranodal-MALT-type, was diagnosed in ou r Department in three cases: Two arose in the orbit and the third one in th e tonsil. The tumors had a typical histologic appearance. The microscopical features and immunohistochemical profile are discussed.