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Biclonal presentation of lymphoplasmacytic lymphoma/Waldenström macroglobulinaemia

2019; Elsevier BV; Volume: 51; Issue: 3 Linguagem: Inglês

10.1016/j.pathol.2018.10.022

1465-3931

Wei Wang, Yi Ding, Andrew Campbell, Beverly C. Handy, L. Jeffrey Medeiros, Pei Lin,

Lymphoma Diagnosis and Treatment

Lymphoplasmacytic lymphoma/Waldenström macroglobulinaemia (LPL/WM) is a lymphoid neoplasm involving bone marrow associated with an IgM paraprotein. It is composed of small lymphocytes, plasmacytoid lymphocytes and plasma cells in variable proportions.1Swerdlow S. Cook J. Sohani A. et al.Lymphoplasmacytic lymphoma.in: Swerdlow S. Campo E. Harris N. Who Classification of Tumours of Haematopoietic and Lymphoid Tissues. IARC Press, Lyon2017: 232-235Google Scholar About 10–20% of patients with LPL/WM have involvement of lymph nodes, spleen or other extranodal sites.2Shaheen S.P. Talwalkar S.S. Lin P. et al.Waldenstrom macroglobulinemia: a review of the entity and its differential diagnosis.Adv Anat Pathol. 2012; 19: 11-27Crossref PubMed Scopus (19) Google Scholar This neoplasm is monoclonal and usually derives from a single transformed B-cell progenitor. In this study, we present an interesting case of LPL/WM with two different clones identified in bone marrow and lymph node, respectively. Whereas MYD88 L265P mutation was detected at both anatomical sites, flow cytometric immunophenotypic analysis and immunohistochemical studies demonstrated kappa light chain restricted cells in the bone marrow but lambda light chain restricted cells in the lymph node. Correspondingly, serum protein electrophoresis and immunofixation studies showed two paraproteins, IgM kappa and IgM lambda. To determine whether these two neoplastic populations in bone marrow and lymph node, respectively, were derived from the same clone, we performed next generation sequencing analysis to study immunoglobulin heavy chain (IGH) chain and kappa light chain (IGK) gene rearrangements. We found that neoplastic cells from bone marrow and lymph node had different V(D)J rearrangements, indicating they were independent clones. Analysis of rearranged IGK sequences from the lymph node revealed the kappa deleting element (kde), which led to inactivation of the IGK allele; as a result, lambda light chain (IGL) was rearranged and transcribed, as demonstrated by lambda light chain expression by lymphoma cells in the lymph node. The patient was a 62-year-old man who presented with anemia (red blood cells 3.68 × 106/μL, haemoglobin 10 g/dL). The white blood cell and platelet counts were normal. Serum studies showed an elevated free kappa/lambda ratio of 8.7 with free kappa of 63 mg/L (3.3–19.4 mg/L) and free lambda of 7.26 mg/L (5.7–26.3 mg/L). IgM was elevated at 3407 mg/dL. Protein electrophoresis and immunofixation studies showed two paraproteins; one was IgM lambda (0.6 g/dL) and another was IgM kappa (2.3 g/dL) (Fig. 1). Positron emission tomography-computed tomography (PET-CT) scan showed right axillary lymphadenopathy (up to 4/4 cm) with a standardised uptake value (SUV) up to 5.3 as well as multiple small retroperitoneal and mesenteric lymph nodes with a SUV of 4.0. There was no evidence of splenomegaly but the spleen showed mild diffuse hypermetabolic activity with a SUV up to 4.8. Hypermetabolic activity was also observed in the axial skeleton with a maximum SUV of 5.8. Bone marrow biopsy showed an atypical lymphoid infiltrate composed of many small lymphocytes and scattered plasma cells in an interstitial and focally diffuse pattern (Fig. 2). By immunohistochemistry, the lymphocytes were predominantly B cells positive for CD20. The anti-CD138 antibody highlighted scattered plasma cells and light chain antibodies showed kappa restriction. Flow cytometric analysis showed an aberrant B cell population, positive for CD19, CD20 and monotypic surface kappa, and negative for CD5 and CD10 (data not shown). A small kappa-restricted plasma cell population was also detected by flow cytometric analysis (data not shown). Molecular study using PCR and a quantitative pyrosequencing method detected a MYD88 L265P mutation with a mutation rate of 16.5%. Lymph node excisional biopsy showed that the nodal architecture was effaced by lymphoma in a vaguely nodular pattern (Fig. 3). The lymphoma was composed of sheets of small lymphocytes and scattered to loosely clustered plasma cells. Immunostain for CD20 highlighted sheets of B cells and CD138 highlighted scattered plasma cells. Kappa and lambda immunostains showed that neoplastic cells were lambda restricted. The concurrent flow cytometric immunophenotyping studies of the lymph node showed an aberrant B-cell population, positive for CD19, CD20 and monotypic surface lambda, and negative for CD5 and CD10 (data not shown). Molecular study detected MYD88 L265P mutation with a mutation rate of 40%. We assessed the lymphoma cells in bone marrow and lymph node for a clonal relationship by performing next generation sequencing (NGS) analysis to study the patterns of gene rearrangements for IGH and IGK using the LymphoTrack assay (Invivoscribe, USA). In the bone marrow, IGH rearrangement showed a dominant clone that utilised VH3-J4 (Fig. 4A). This same clone was also identified in the lymph node but was significantly smaller; instead a different dominant clone was identified which utilised VH3-J5 (Fig. 4B). Sequence comparison showed no similarity between these two dominant clones. Analysis of the rearranged IGK in bone marrow and lymph node also showed different dominant clones (Fig. 4C versus 4D). Further analysis of the dominant IGK clone from lymph node revealed the kde rearranged to the Jk-Ck intron (IGKintr-IGKdel, Fig. 4D). The rearrangement involving kde has been shown to inactivate the IGK allele through deletion of the entire Jk-Ck area or the Ck region only.3Gonzalez D. van der Burg M. Garcia-Sanz R. et al.Immunoglobulin gene rearrangements and the pathogenesis of multiple myeloma.Blood. 2007; 110: 3112-3121Crossref PubMed Scopus (140) Google Scholar The inactivation of IGK triggered subsequent IGL rearrangement and lambda light chain expression in the lymph node. LPL/WM is believed to be a monoclonal process arising from a single transformed progenitor cell which proliferates and differentiates into a heterogeneous population composed of lymphocytes, plasmacytoid lymphocytes and plasma cells. Similar to other haematopoietic diseases, however, clonal heterogeneity and clonal evolution from a common ancestor clone have been described in LPL/WM.4Ciric B. VanKeulen V. Rodriguez M. et al.Clonal evolution in waldenstrom macroglobulinemia highlights functional role of B-cell receptor.Blood. 2001; 97: 321-323Crossref PubMed Scopus (36) Google Scholar In addition, two unrelated clones present in bone marrow and peripheral blood from the same patient have been rarely described.5Bonewald L. Virella G. Wang A.C. Evidence for the biclonal nature of a Waldenstrom's macroglobulinemia.Clin Chim Acta. 1985; 146: 53-63Google Scholar, 6Schulz R. David D. Farkas D.H. et al.Molecular analysis in a patient with waldenstrom's macroglobulinemia reveals a rare case of biclonality.Mol Diagn. 1996; 1: 159-166Crossref PubMed Scopus (9) Google Scholar, 7Kriangkum J. Taylor B.J. Treon S.P. et al.Molecular characterization of Waldenstrom's macroglobulinemia reveals frequent occurrence of two B-cell clones having distinct IGH VDG sequences.Clin Cancer Res. 2007; 13: 2005-2013Crossref PubMed Scopus (20) Google Scholar Here we have presented a unique case of biclonal LPL/WM with different clones located in bone marrow and lymph node, respectively. Biclonality was shown at both the protein and molecular levels. Although two paraproteins (IgM kappa and IgM lambda) were detected in the serum, the predominant paraprotein was IgM kappa which was derived from neoplastic cells in bone marrow. The presence of two different clones carrying the same MYD88 L265P mutation raises the possibility that the MYD88 mutation occurred before VDJ rearrangements, although the emergence of two MYD88 L265P mutations independently later after VDJ rearrangements can not be completely excluded. The authors state that there are no conflicts of interest to disclose.