Nodal marginal zone B-cell lymphoma: a diagnostic and therapeutic dilemma.

In the last lymphoma classifications, three types of marginal zone lymphoma (MZL) were delineated: extranodal mucosa-associated lymphatic tissue (MALT) lymphoma, splenic MZL, and nodal MZL (NMZL). While MALT lymphoma is already well characterized and has been extensively studied, the pathogenesis of the other two types, especially that of NMZL, remains incompletely understood. The tumor is rather uncommon, although it shares morphologic and immunophenotypic similarities with the other MZLs. Few series have been published, and the description is quite heterogeneous, reflecting the lack of consensus criteria for its diagnosis; the ability to develop such criteria is impeded by the absence of specific immunological or molecular abnormalities. The disease develops from peripheral (mostly cervical) and abdominal lymph nodes, with or without bone marrow and blood involvement. How to differentiate NMZL from lymphoplasmacytic lymphoma remains a key point of debate. NMZL also represents a therapeutic dilemma, given the absence of published large or prospective series. The 5-year overall survival as well as the failure-free survival of patients appear to be lower than those of patients with extranodal MZL.The aim of this review is twofold: to summarize descriptions of the clinical presentation provided in published series in order to help clinicians recognize and treat patients, and to discuss diagnostic difficulties faced by hematopathologists when dealing with these lesions and others in the differential diagnosis that must be distinguished from one another.