Abstract:Objective To investigate the clinicopathological features of lymphoplasmacytic lymphoma (LPL) in order to improve the pathologic diagnosis and differential diagnosis of LPL.Methods Three LPL patients were analyzed retrospectively based on clinical,laboratory,and pathological data,flow cytometry and MYD88 L265P fusion gene mutation.Results There were 1 male and 2 female patients with a median age of 69 years.There were 1 case of splenomegaly and 2 cases of lymphadenopathy.All patients had anemia,hyperviscosity and elevated beta 2 microglobulin.Monoclonal IgM κ and monoclonal IgM λ were identified in 2 cases and 1 case,respectively.Flow cytometry of bone marrow showed that abnormal B lymphocytes accounted for 2.05% of nuclear cells,with a restricted expression of λ and CD5+ CD10- monoclonal B cell phenotype,and abnormal plasma cells accounted for 0.64% of nuclear cells,with a restricted expression of Lambda in one case.In the other case,abnormal lymphocytes accounted for 10.89% of the nuclear cells,with a CD5- CD10- monoclonal B cell phenotype and restricted κ expression.MYD88 L265P mutation was positive in 2 cases and negative in 1 case.Bone marrow biopsies showed that there were many small lymphocytes,plasmacytoid lymphocytes and plasma cells in trabecular bone,showing interstitial or nodular infiltration in 3 cases.Immunohistochemistry showed that some infiltrated small lymphocytes were positive for CD20,CD38,CD138 and MUM1 (specific transcription factor) and were negative for CD5,CD10 and CD23.In cervical lymph node biopsy for one case,HE section displayed that dilated lymphatic sinuses were filled with pink-stained lymphatic fluid,blurred margin nodules were composed of medium-sized lymphocytes,with focal distribution of plasma cells in the subcapsular sinus and beside the lymphatic sinus,and a small number of mast cells,immunoblasts,epithelioid cells and hemosiderin deposition were scattered among the tumor cells.Immunohistochemically,CD20,CD79a and BCL2 were expressed diffusely,CD10 and BCL6 were expressed in residual germinal center,CD21 and CD23 were expressed in irregular follicular dendritic cell′s network and a small number of plasma cells revealed CD38,CD138 and MUM1,with a restricted expression of λ.The count of Ki-67 cells was about 10%,and CyclinD1 and EBER were negative.Conclusion LPL is usually found by bone marrow biopsy,and only a few cases are diagnosed by lymph node biopsy.All clinical data (history of disease,laboratory examination and imaging),morphology,immunohistochemistry and flow cytometry are helpful to accurate pathological diagnosis.If necessary,MYD88 L265P mutation should be detected.