OBJECTIVETo study the morphologic features, immunophenotype, differential diagnosis and prognosis of nodal marginal zone B-cell lymphoma (NMZL).

METHODSLight microscopic examination and immunohistochemical study were carried out in 10 cases of NMZL. Seven of which had follow-up information available.

RESULTSAll cases presented with good performance status at the time of diagnosis. Amongst the 7 cases with follow-up information available, most (6/7) were in advanced clinical stage (stage II to III). The one-year survival rate was 67%. A vaguely nodular growth pattern was observed in most cases of NMZL (5/10). The lymphoma was composed predominantly of atypical lymphoid cells resembling centrocytes (7/10). A predominance of monocytoid B-cell (2/10) or small lymphocytic (1/10) morphology was rare. Instead, the presence of a minor component of monocytoid B cells was not uncommon (5/10). Plasmacytoid or plasmacytic cells were also frequently found (8/10). The proliferation index ranged from 5% to 50%. Follicular dendritic cells appeared atrophic in 7 cases and variably hyperplasic in 3 cases.

CONCLUSIONSPrimary NMZL is rare. It has a unique growth pattern and most cases are composed predominantly of cells resembling centrocytes. Differential diagnosis includes lymphoplasmacytic lymphoma, lymph node involvement by extranodal marginal zone B-cell lymphoma and T-zone hyperplasia. The clinical stage is often high at presentation, with systemic dissemination. The prognosis of NMZL is thus relatively poor.