BACKGROUNDTo study the clinicopathologic and immunohistochemical features of primary pulmonary extranodal marginal zone B-cell lymphomas (MALT lymphomas).

METHODSImmunohistochemical staining for LCA, CD20, CD45RO, CD5, cyclinD1, Ki-67, immunoglobine light chain κ and λ, CK and NSE was carried out in 9 patients with primary pulmonary extranodal marginal zone B-cell lymphomas by the S-P methods.

RESULTSAccording to the histological pattern and immunohistochemical features, all patients were diagnosed as primary pulmonary extranodal marginal zone B-cell lymphomas. There were four males and five females with a median age of 51.5 years (range from 37 to 64 years). The tumor cells were positive for LCA and CD20, however, the positive rates of Ki-67 were low. The tumor cells expressed immunoglobine light chain restriction λ in 5 cases , κ in 1 case, both λ and κ in 1 case, and neither of them in 2 cases. The tumor cells were negative for CD45RO, CD5, cyclineD1, CK, NSE in all patients.

CONCLUSIONSPrimary pulmonary extranodal marginal zone B-cell lymphomas are inert lymphomas which are easily misdiagnosed. The evaluation of pathologic features and immunohistochemistry are useful and practical in the diagnosis and differential diagnosis of primary pulmonary extranodal marginal zone B-cell lymphomas.