Nodal Marginal Zone Lymphoma

General: Nodal marginal zone lymphoma is an uncommon lymphoma, comprising approximately 2% of NHL. There is a slight female predominance (M:F = 0.7) and the median age at diagnosis is 58 years. Forty percent of patients have marrow involvement at presentation and the overall survival is approximately 55% at 5 years.1 In order to make this diagnosis, patients should not have previous or concurrent extra-nodal marginal zone lymphoma of MALT type.

Pathology: The lymph node is altered by an infiltrate of marginal zone cells. These cells are small with condensed chromatin, slightly irregular nuclei, and variable amounts of pale cytoplasm. The cells, therefore, can vary between centrocyte-like cells and monocy-toid B-cells. Plasmacytic differentiation can be seen in some cases. The infiltrate expands the interfollicular areas with preservation of reactive germinal centers

Figure 52.10 Nodal marginal zone B-cell lymphoma showing a germinal center (arrows) that is ill-defined and being infiltrated by lymphoma cells

(Figures 52.10 and 52.11). Colonization of the follicles can occur and impart a nodular appearance to the lymphoma. Two subtypes have been suggested, a MALT type and splenic type, based on resemblance to these two lymphomas.51

Immunophenotype: This lymphoma expresses CD19, CD20, and surface immunoglobulin. CD5 or CD10 are not expressed. Some cases express IgD and this has been suggested as a differentiating characteristic between the splenic type (positive) and the MALT type (negative).51 Molecular genetics: Little is known regarding the molecular genetics of this lymphoma. It has been shown that these lymphomas do not contain MLT1 translocations, supporting the concept that these lymphomas are distinct from MALT lymphomas.34

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