Lymphoplasmacytic lymphoma with IgG or IgA paraprotein: a study of 29 cases including cases that can mimic plasma cell neoplasms

A Rare Case of Non-IgM Lymphoplasmacytic Lymphoma with Unusual Lack of Immunoglobulin Light Chain Production

“…Flow cytometry analysis of the B lymphocytes and plasma cells from non-IgM LPL consistently show monotypic concordant immunoglobulin light chain expression between these 2 components. In one series study [ 6 ], the neoplastic plasma cells defined by bright CD38 and CD138 were almost always positive for CD45 (100%, 26/26) and CD19 (96%, 25/26), while only partial/weak positive for CD56 (16%, 4/25), and negative for CD117 (100%, 24/24). In contrast, plasma cell neoplasm cells commonly show loss of CD19 and CD45 and gain of aberrant expression of CD56 and CD117 in about 70% and 30% cases, respectively.…”

“…The gene mutation data in non-IgM LPL is relatively scarce, and recent studies suggest MYD88 and CXCR4 mutations are possibly the 2 most recurrent gene mutations, similar to WM. Limited data indicate the prevalence of a MYD88 mutation in non-IgM LPL is about 43% to 80%, appearing to be lower than in WM [ 1 – 4 , 6 ]. Approximately 25% to 33% of the non-IgM LPL cases harbor a CXCR4 mutation, which frequently co-occurs with MYD88 mutation (67–75% concurrence rate) [ 3 , 6 ].…”

“…Limited data indicate the prevalence of a MYD88 mutation in non-IgM LPL is about 43% to 80%, appearing to be lower than in WM [ 1 – 4 , 6 ]. Approximately 25% to 33% of the non-IgM LPL cases harbor a CXCR4 mutation, which frequently co-occurs with MYD88 mutation (67–75% concurrence rate) [ 3 , 6 ]. Both MYD88 and CXCR4 mutations are not entirely specific for WM and non-IgM LPL and can be also detected in many other B-cell lymphomas [ 14 ].…”

“…Careful clinicopathologic correlation aided by ancillary tests, especially the molecular mutational landscape, can be instrumental in this differential diagnosis. Literature shows CXCR4 mutation occurs in approximately 25% to 33% of non-IgM LPL cases [ 3 , 6 ]; its mutation status in the other small B-cell lymphomas, however, has been rarely investigated. Searching through the literature reveals available data only in 3 recent studies for MZL [ 15 – 17 ].…”

“…A paraprotein other than IgM is often detected in non-IgM LPL, and the presence of IgG paraprotein is the most likely type, followed by IgA. Non-secretory non-IgM LPL is not common, accounting for about 0% to 13% of the studied cases [ 1 – 4 , 6 ]. Flow cytometry analysis of the non-IgM LPL cases in the literature indicates the B cells mostly demonstrate monotypic surface light chain, with kappa being the more frequently expressed light chain.…”