Primary Splenic and Nodal Marginal Zone Lymphoma

Primary splenic and nodal marginal zone (MZ) lymphomas are rare small B cell lymphomas presenting with similar histopathologic features. The neoplastic cell population mostly consists of monocytoid B cells organized in a MZ pattern, associated with centrocytoid cells colonizing follicles. About 50% of cases have a monotypic plasma cell component. The different histopathologic patterns and differential diagnosis are discussed here. Both diseases share a similar immunophenotype, with the expression of B-cell associated antigens and restriction of immunoglobulin light chain. The only difference is the more frequent expression of IgD in splenic than in nodal lymphomas. The most recent findings in genetics and molecular biology are presented and discussed. The main clinical and biological symptoms are described and the similarity of some cases with Waldenstro "ms macroglobulinemia is stressed. Both lymphomas present with the same type of bone marrow involvement with a high frequency of intravascular infiltrates, which can be associated with interstitial and nodular infiltrates. Transformation into diffuse large B cell lymphoma occurs in about 10 to 15% of the cases. The outcome in many splenic MZ lymphomas is characterized by a lengthy survival after splenectomy (9 to 13 years or longer), despite the absence of a consensus on the optimal treatment. Nodal MZ lymphoma has a more aggressive evolution and seems to only be curable at an early stage. Further studies are needed of both lymphomas to improve treatment and prognosis.