ABSTRACT
In the mid-1990s, mucosa-associated lymphoid tissue (MALT) lymphomas were classified together with two other related entities, the nodal marginal zone lymphomas (MZL) and splenic MZL. A series of specific chromosomal translocations have been exclusively identified in extranodal marginal zone B-cell lymphoma (EMZL), identifying EMZL as a separate entity. EMZL cells almost always bear a pattern of somatic hypermutation and rearrangement suggesting that the cell of origin appears to be a postgerminal center marginal zone B cell. The tumor cell has undergone antigen selection in germinal centers and can continue to be at least partially driven by direct antigen stimulation. Since the several translocations are highly specific for EMZL, their demonstration can be useful in the differential diagnosis of MALT lymphomas vs other small cells lymphomas involving extranodal sites. Differently from chronic lymphocytic leukemia, the analysis of the immunoglobulin heavy chain mutational status has no prognostic role in EMZL.
