MYD88 p.L265P and CD79B p.Y196C/H mutations were analyzed in diffuse large B-cell lymphoma (DLBCL) patients whose tumor samples were available (N = 29).
Heterozygous MYD88 L265P mutations were identified in 11 (9.2%) DLBCL cases, all of which were diagnosed as non-germinal-center B cell (non-GCB) DLBCL.
High frequencies of the hotspot <i>MYD88</i>(L265P) mutation are observed in extranodal diffuse large B-cell lymphoma and Waldenström macroglobulinemia, thereby demonstrating this mutation's potential as a disease marker.
MYD88 L265P is the most common mutation in lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) and one of the most frequent in poor-prognosis subtypes of diffuse large B-cell lymphoma (DLBCL).
<i>Results</i>: MYD88 L265P mutations were detected in 22 of 29 samples from 14 patients with diffuse large B-cell lymphomas and one patient with lymphoplasmacytoid lymphoma.
Primary DLBCL in sanctuary sites (DLBCL-SS) also demonstrates these features, and >70% of patients harbor myeloid differentiation primary response 88 (MYD88) (L265P) and CD79B mutations.
Recent studies demonstrated that in the activated B cell subtype of diffuse large B cell lymphoma (DLBCL), approximately one-third of the patients harbored somatically acquired MyD88 L265P mutation in their lymphomas.
A missense mutation (L265P) changing leucine at position 265 to proline in MYD88 is found in ∼90% of Waldenström macroglobulinemia (WM) cases and in significant portions of activated B-cell diffuse large B-cell lymphomas and IgM monoclonal gammopathy of undetermined significance.
Also, MYD88L265P had little involvement in GI DLBCL compared with other extranodal DLBCLs, suggesting that its pathogenesis might be different from that of organs with a high frequency of MYD88 L265P.
Finally, although the MYD88 L265P variant was not an independent prognostic factor in ABC DLBCL, associated <i>CD79B</i> mutations significantly improved the survival of MYD88 L265P-mutant ABC DLBCL in our cohort.<b>Conclusions:</b> This study highlights the relative heterogeneity of <i>MYD88</i>-mutant DLBCL, adding to the field's knowledge of the theranostic importance of <i>MYD88</i> mutations, but also of associated alterations, emphasizing the usefulness of genomic profiling to best stratify patients for targeted therapy.<i></i>.
We identified the MYD88 L265P somatic variant in cases with WM (39/42), MGUS (8/18), NHL (14/41, including 4/13 diffuse large B cell lymphoma (DLBCL), 1/8 mucosa-associated lymphoid tissue, 3/6 splenic marginal zone lymphoma (SMZL), 1/4 chronic lymphocytic leukemia, 2/3 nodal marginal zone lymphoma (NMZL), 1/2 mantle cell lymphoma, 1 Burkitt lymphoma, and 1 B cell NHL that could not be classified), primary AL (2/2), and IgM-PN (1/1).