Pathology of extranodal marginal zone lymphoma at different anatomic sites

Abstract

: Extranodal marginal zone lymphomas arise within acquired lymphoid tissue at a variety of extranodal sites. They have characteristic architectural and morphological features that recapitulate those seen in constitutive lymphoid tissue in extranodal locations that is best exemplified by the mucosa (gut) associated lymphoid tissue (MALT) present as Peyer’s patches in the terminal ileum. The morphology of these MALT lymphomas is constant across the various extranodal sites in which they are encountered although there is some variation between cases in the detailed cellular morphology with variable proportions of cells with centrocyte-like, monocytoid and plasmacytoid/plasmacytic appearances. Architecturally there is inter-case variation in the degree and type of follicular colonisation. The appearance of lymphoepithelial lesions varies between sites. There is variable association with light chain deposition disease and nodular amyloidosis which appear to be more frequently associated with a pulmonary origin. The immunophenotype is uniform across sites with a rather non-specific B-cell antigen expression with aberrant CD43 expression in a proportion of cases. There is infrequent expression of CD5 and this appears more frequent in lymphomas arising in the ocular/ocular adnexal region.