Marginal zone-related neoplasms of splenic and nodal origin

Background. The marginal zone is an anatomically distinct B-cell compartment of lymphoid tissue with an abundant antigenic influx. Among marginal zone-derived lymphomas the WHO classification listed, in addition to extranodal marginal zone B-cell lymphoma of MALT type, two other marginal zone B-cell neoplasms: splenic marginal zone B-cell lymphoma (+/- villous lymphocytes) and nodal marginal zone B-cell lymphoma (+/- monocytoid B cells). These two entities are well characterized histologically, but specific biological markers are lacking. Treatment options are heterogeneous, including a watch-and-wait policy, surgery with or without chemotherapy, purine analogs, and interferon. No prospective studies have been conducted so far. Information sources. Clinical and pathologic data were reviewed by searches of the published medical literature, including searches in PubMed(R), important printed publications, and abstracts presented at recent hematology and pathology meetings. State of the art. Splenic and nodal marginal zone lymphomas are typical low-grade lymphomas with an indolent course. A subset of patients, however, presents with more aggressive disease and have a shorter survival. Clinical and biological prognostic factors identified in reported series are heterogeneous. The role played by hepatitis C virus (HCV) in marginal zone lymphomas is not fully elucidated, but there is demonstration that eradication of HCV infection in splenic lymphoma with villous lymphocytes causes regression of the lymphoma. The optimal treatment has not yet been identified. Retrospective series, however, show that splenectomy is a good option if symptoms from the presence of spleen enlargement or cytopenias need to be treated. The utility of purine analogs and of anti-CD20 immunotherapy needs to be clarified in prospective trials. Perspectives. Clinicians and pathologists should cooperate to define stringent diagnostic criteria for these indolent disorders. The optimal therapeutic approach and the role of new treatments need to be assessed in prospective clinical trials.