Pathology of nodal marginal zone lymphomas

Marginal zone B-cell lymphoma: lessons from Western and Eastern diagnostic approaches

“…20,141 Plasma cell differentiation may be prominent, posing a problem for differential diagnosis from lymphoplasmacytic lymphoma, nodal plasmacytoma, and IgG4-related lymphadenopathy. [142][143][144][145] As indicated previously, 136 the large tumour cells are more frequently admixed than in SMZL and MALT lymphoma, which often raises the question of whether it should be diagnosed as NMZL or DLBCL histological transformation or evolution. If no overt or sheet-like proliferation of large cells is present, the preferable diagnosis of NMZL is recommended because the proportion of scattered or clustered large cells or the Ki-67 index appear to have little prognostic significance.…”

“…WHO lymphoma classification defines NMZL as a primary nodal B-cell neoplasm that morphologically resembles the extranodal (MALT) or splenic MZL types, but patients lack clinical evidence of extranodal or splenic disease. 136,137 Bone marrow involvement occurs in 30-40% of patients. This disease is challenging for pathologists to recognise because of the lack of exclusive positive immunohistochemical or molecular markers.…”

“…This disease is challenging for pathologists to recognise because of the lack of exclusive positive immunohistochemical or molecular markers. 136,138 NMZL is known to be heterogeneous, with greater variability in growth pattern and cellular morphology in comparison with other types of MZL.…”

“…This lymphoma is now subdivided according to its growth pattern, the histological diversity of which has been well documented in the past two decades. 4,136,138 In 1999, Campo et al first described two variants of NMZBL, splenic type (sNMZL) (n=6) and MALT type (mNMZL) (n=30), which are identified based on phenotypical and morphological findings reminiscent of SMZL and MALT lymphoma, respectively. This implies that sNMZLs and mNMZLs are indistinguishable from secondary nodal involvement of SMZL and MALT lymphoma, respectively, based on their histopathological findings and without an accurate clinicopathological correlation.…”

“…The tumour cells are of small to intermediate size and usually have a monocytoid appearance with abundant pale cytoplasm and round to irregular nuclei. 136 In sNMZL, tumour cells selectively involve germinal centres or grow in close proximity to a germinal centre without effacing the lymph node architecture, posing a problem for differential diagnosis with follicular lymphoma (Fig. 6).…”