Objective: To study the clinicopathologic features, diagnosis and differential diagnosis of splenic marginal zone B-cell lymphoma (SMZL).
Methods: The clinical data, histologic findings and immunophenotype of 8 SMZL cases were studied. IgH gene rearrangement was performed in 1 case. Follow-up information was available in 4 patients.
Results: The median age of the patients was 61.5 years (range: 36 to 75 years). The male-to-female ratio was 1.7:1. All cases presented with massive splenomegaly. Five of six cases had abnormal blood counts: neutropenia and thrombocytopenia with two of them showing anemia. After splenectomy, the blood counts in 3/3 cases returned to normal levels. Post-operative fludarabine-based chemotherapy was given to 3 patients, two of them achieved complete remission and 1 case died during the course of chemotherapy. The average survival time was 21.5 months (range: 6 to 60 months). Histologically, all of the 8 cases showed micronodular white pulp lesions. Six of them exhibited the classic biphasic appearance with central aggregates of small B cells rimmed by a peripheral zone of atypical monocytoid B cells. The remaining 2 cases had a monomorphous appearance, consisting mainly of atypical monocytoid B cells. There was infiltration of tumor cells in the red pulp, sheets in appearance in all 8 cases. Immuno-histochemical staining showed CD20-positive (8/8), IgD-positive in 2 of the 4 cases (2/4), CD5-positive in 1 of the 4 cases (1/4), 6 of the 6 cases were bcl-2-positive, cyclin D1-negative and bcl-6/CD10-negative, CD43-negative in 5 of the 6 cases (5/6). The proliferation index, as highlighted by Ki-67 immunostaining, was low (< 15%).
Conclusions: SMZL is an indolent B-cell non-Hodgkin lymphoma. The main clinical manifestations are splenomegaly and abnormalities in blood counts. The main modality of treatment is splenectomy. Adjuvant fludarabine-based chemotherapy helps to achieve complete remission. In general, the prognosis of this lymphoma type is good. The lymphoma cells predominantly grow in micronodular pattern, with atypical monocytoid B cells rimming around the small B cells, which aggregates in the center. The differential diagnosis includes other small B-cell lymphomas and lymphoid hyperplasia of spleen.