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

A high proportion of extranodal lymphoid infiltrates are diffuse small lymphocytic proliferations [1, 2] and therefore pose a particularly challenging diagnostic problem [1-4]. Their benign or malignant nature cannot be determined using clinical and radiologic criteria. The application of traditional morphologic criteria (i.e., cytologic maturity and polymorphism favor benignancy, while cytologic atypia and monomorphism favor malignancy) [5, 6], has probably improved diagnostic accuracy. However, these criteria generally have not been helpful in evaluating the large number of lymphoid infiltrates composed of monomorphic collections of small cytologically-mature appearing lymphoid cells [1-4] and, therefore, have not always accurately predicted clinical behavior. Extranodal lymphoid proliferations are also of considerable biologic interest since their pathogenesis and natural history have not been fully elucidated. Localized non-Hodgkin's lymphoma, extranodal-MALT-type. was diagnosed in our Department in three cases: Two arose in the orbit and the third one in the tonsil. The tumors had a typical histologic appearance. The microscopical features and immunohistochemical profile are discussed.