{"entity":{"id":"cd79b-itam-mutation","kind":"biomarker","name":"CD79B ITAM mutation","aka":["CD79B mutation","CD79B Y196","CD79A ITAM mutation","ITAM mutation"],"tldr":"A change in the signalling tail of part of the B-cell receptor that leaves the receptor switched on without needing anything to bind it. It marks a group of large B-cell lymphomas that depend on that signal, and therefore on the enzyme BTK.","summary":"The B-cell receptor signals through the ITAM motifs of CD79a and CD79b. In activated B-cell-like diffuse large B-cell lymphoma, the receptor signals continuously: the receptors form slow-diffusing clusters in the membrane like those of an antigen-stimulated normal B cell, and knocking down IgM, Ig-kappa, CD79A, CD79B or BTK kills the cell while leaving other lymphomas alone. Somatic mutations of the ITAM modules were detected frequently in activated B-cell-like biopsies, rarely in other diffuse large B-cell lymphomas and never in Burkitt or MALT lymphoma; the mutations raise surface receptor expression and blunt LYN, the kinase that normally damps the signal down (Davis 2010).\n\nCD79B mutation with MYD88 L265P is what names the MCD genetic subtype (Schmitz 2018). CD79b protein itself is expressed on more than 95% of diffuse large B-cell lymphomas regardless of mutation status, which is why polatuzumab vedotin, the anti-CD79b conjugate, is given without a test.","asOf":"2026-09-30","links":[{"label":"Davis et al., Nature 2010: chronic active B-cell receptor signalling in diffuse large B-cell lymphoma","url":"https://doi.org/10.1038/nature08638"},{"label":"Schmitz et al., N Engl J Med 2018: genetics and pathogenesis of diffuse large B-cell lymphoma (574 biopsies; MCD, BN2, N1, EZB)","url":"https://doi.org/10.1056/NEJMoa1801445"}],"tags":["biomarker","lymphoma"],"related":["myd88-l265p"],"cancers":["dlbcl","primary-cns-lymphoma","non-hodgkin-lymphoma"],"sections":[],"technologies":["cgp"],"targets":["cd79b","btk","myd88"],"drugs":["ibrutinib","polatuzumab-vedotin"],"companies":[],"institutions":[],"pathways":["bcr-signalling","inflammation-nfkb"],"terms":["lymphoma-bio-lymphgen","cell-of-origin","ngs"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"target":"cd79b","measurement":"sequencing-variant","scoringRule":{"text":"Targeted sequencing of the CD79B ITAM region, reported as mutated or wild-type, usually as part of a lymphoma gene panel rather than alone. It is a different question from CD79b protein expression, which is near-universal in large B-cell lymphoma and is not tested before polatuzumab vedotin.","quote":"In 18% of ABC DLBCLs, one functionally critical residue of CD79B, the first ITAM tyrosine, was mutated.","source":"https://doi.org/10.1038/nature08638","sourceLabel":"Davis et al., Nature 2010"},"thresholds":[],"definedBy":{"label":"Schmitz et al., N Engl J Med 2018: genetics and pathogenesis of diffuse large B-cell lymphoma (574 biopsies; MCD, BN2, N1, EZB)","url":"https://doi.org/10.1056/NEJMoa1801445"},"tests":[],"assays":[],"companionDiagnostics":[],"forPatient":"This result does not change a licensed treatment today. Together with MYD88 it puts a lymphoma in the group that has shown the most response to BTK inhibitor drugs in research studies, so it may make a trial relevant."},"route":"/biomarkers/cd79b-itam-mutation/","neighbours":{"term":[{"id":"cell-of-origin","kind":"term","name":"Cell of origin (GCB vs ABC)","route":"/terms/cell-of-origin/"},{"id":"lymphoma-bio-lymphgen","kind":"term","name":"LymphGen and the genetic clusters of large B-cell lymphoma","route":"/terms/lymphoma-bio-lymphgen/"},{"id":"myd88-l265p","kind":"term","name":"MYD88 L265P and CXCR4 mutations","route":"/terms/myd88-l265p/"},{"id":"ngs","kind":"term","name":"Next-generation sequencing (NGS)","route":"/terms/ngs/"}],"cancer":[{"id":"dlbcl","kind":"cancer","name":"Diffuse large B-cell lymphoma","route":"/cancers/dlbcl/"},{"id":"non-hodgkin-lymphoma","kind":"cancer","name":"Non-Hodgkin lymphoma (all types)","route":"/cancers/non-hodgkin-lymphoma/"},{"id":"primary-cns-lymphoma","kind":"cancer","name":"Primary CNS lymphoma","route":"/cancers/primary-cns-lymphoma/"}],"technology":[{"id":"cgp","kind":"technology","name":"Comprehensive genomic profiling","route":"/technologies/cgp/"}],"target":[{"id":"btk","kind":"target","name":"BTK (Bruton tyrosine kinase)","route":"/targets/btk/"},{"id":"cd79b","kind":"target","name":"CD79b","route":"/targets/cd79b/"},{"id":"myd88","kind":"target","name":"MYD88","route":"/targets/myd88/"}],"drug":[{"id":"ibrutinib","kind":"drug","name":"Ibrutinib","route":"/drugs/ibrutinib/"},{"id":"polatuzumab-vedotin","kind":"drug","name":"Polatuzumab vedotin","route":"/drugs/polatuzumab-vedotin/"}],"pathway":[{"id":"bcr-signalling","kind":"pathway","name":"B-cell receptor / BTK signalling (to NF-κB)","route":"/pathways/bcr-signalling/"},{"id":"inflammation-nfkb","kind":"pathway","name":"Inflammation & NF-κB","route":"/pathways/inflammation-nfkb/"}]}}