Eosinophil‐rich variant of nodal marginal zone lymphoma: a clinicopathological study of 11 cases

Aims Tissue eosinophilia is commonly observed in T‐cell and classic Hodgkin lymphomas, but rarely in B‐cell lymphomas. Herein, we present the first report of a case series on nodal marginal zone lymphoma (NMZL) with tissue eosinophilia. Methods and results All 11 patients in this study had nodal disease at primary presentation. The mean age at diagnosis was 64 years. The mean follow‐up period was 39 months, and all patients were alive. Nine of the 11 patients (82%) showed no recurrence, but the other two patients experienced recurrence in the lymph nodes or skin. Marked eosinophilic infiltration was observed in all biopsied lymph nodes. Nine of the 11 patients had a preserved nodular architecture with expanded interfollicular areas. The other two patients showed diffuse lymphoma cell infiltration with effacement of nodal architecture. One of them was diagnosed as having diffuse large B‐cell lymphoma transformed from NMZL because large cells accounted for >50% of the lymphoma cells and formed sheet‐like patterns. Cells were positive for CD20 and BCL2 and negative for CD5, CD10, and BCL6. Some patients showed myeloid cell nuclear differentiation antigen (MNDA) positivity. All patients showed B‐cell monoclonality via flow cytometry, southern blotting, and/or polymerase chain reaction (PCR). Conclusion All patients showed distinctive morphological features and could be misdiagnosed with peripheral T‐cell lymphoma due to their eosinophil‐rich backgrounds. The predominance of B cells, absence of histiocytes, and high endothelial venules in the interfollicular areas are key factors for diagnosis. B‐cell monoclonality is the most reliable evidence of differentiation. We designated this type of lymphoma as an eosinophil‐rich variant of NMZL.