{"entity":{"id":"cd20-expression","kind":"biomarker","name":"CD20 expression (CD20-positive)","aka":["CD20-positive","CD20+","CD20 expression","CD20 positive lymphoma","CD20 loss"],"tldr":"CD20 is the B-cell antigen rituximab made famous. Rituximab and obinutuzumab labels are written for CD20-positive lymphoma and leukaemia; the newer CD20 x CD3 bispecifics assume it.","summary":"CD20 is read by immunohistochemistry or flow cytometry and is present on almost all mature B-cell lymphomas and chronic lymphocytic leukaemia. Rituximab (Rituxan) is labelled as a CD20-directed cytolytic antibody for CD20-positive non-Hodgkin lymphoma and CLL; obinutuzumab (Gazyva) for CLL and follicular lymphoma; mosunetuzumab, glofitamab and epcoritamab are CD20 x CD3 bispecifics labelled by histology. CD20-negative lymphomas (some after rituximab, and entities such as plasmablastic lymphoma) are excluded from the anti-CD20 indications.","asOf":"2026-09-23","links":[{"label":"Rituxan prescribing information (DailyMed)","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b172773b-3905-4a1c-ad95-bab4b6126563"},{"label":"Hiraga et al., Blood 2009: CD20-negative transformation after rituximab-containing chemotherapy (19 rebiopsied patients)","url":"https://doi.org/10.1182/blood-2008-08-175208"}],"tags":["biomarker","surface-antigen"],"related":["cd19-expression","cd22-expression"],"cancers":["non-hodgkin-lymphoma","dlbcl","follicular-lymphoma","cll","mantle-cell-lymphoma","marginal-zone-lymphoma"],"sections":[],"technologies":[],"targets":[],"drugs":["rituximab","obinutuzumab","mosunetuzumab","glofitamab","epcoritamab"],"companies":[],"institutions":[],"pathways":[],"terms":["ihc","flow-cytometry","antigen-escape","lymphoma-bio-antigen-escape","lymphoma-bio-lineage-antigen-cost"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":["Lymphoma: the stain is part of every diagnostic panel and is not repeated before each dose of rituximab, which is why loss at relapse is under-measured. Of 124 patients treated with rituximab-containing chemotherapy, 36 relapsed or progressed, 19 were rebiopsied and 5 of those, 26.3%, had become CD20-negative, with lower CD20 messenger RNA in the negative cells than in the positive cells from the same patient; all five died within a year (Hiraga 2009). The practical rule is to rebiopsy and restain before giving another CD20-directed drug. CD20 is not internalised, so it carries naked antibodies and T-cell engagers but no antibody-drug conjugate."],"target":"cd20","measurement":"ihc-score","scoringRule":{"text":"CD20 detected on lymphoma or leukaemia cells by immunohistochemistry or flow cytometry; the labels state CD20-positive without a percentage.","quote":"RITUXAN is a CD20-directed cytolytic antibody indicated for the treatment of: Adult patients with Non-Hodgkin's Lymphoma (NHL)","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b172773b-3905-4a1c-ad95-bab4b6126563","sourceLabel":"Rituxan prescribing information"},"thresholds":[{"value":"CD20-positive","drugId":"rituximab","cancerId":"non-hodgkin-lymphoma","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b172773b-3905-4a1c-ad95-bab4b6126563","quote":"RITUXAN is a CD20-directed cytolytic antibody indicated for the treatment of: Adult patients with Non-Hodgkin's Lymphoma (NHL)","status":"current","note":"The full indication text specifies CD20-positive follicular, low-grade and diffuse large B-cell lymphoma and CD20-positive CLL."}],"tests":[],"assays":[],"companionDiagnostics":[],"forPatient":"A CD20-positive result is expected in nearly every B-cell lymphoma and means rituximab or obinutuzumab will be part of treatment, with the CD20-directed bispecific antibodies as later options. A CD20-negative result, which can happen after previous rituximab, steers the team to drugs aimed at other targets."},"route":"/biomarkers/cd20-expression/","neighbours":{"biomarker":[{"id":"cd19-expression","kind":"biomarker","name":"CD19 expression (CD19-positive)","route":"/biomarkers/cd19-expression/"},{"id":"cd22-expression","kind":"biomarker","name":"CD22 expression (CD22-positive)","route":"/biomarkers/cd22-expression/"}],"cancer":[{"id":"cll","kind":"cancer","name":"Chronic lymphocytic leukaemia","route":"/cancers/cll/"},{"id":"dlbcl","kind":"cancer","name":"Diffuse large B-cell lymphoma","route":"/cancers/dlbcl/"},{"id":"follicular-lymphoma","kind":"cancer","name":"Follicular lymphoma","route":"/cancers/follicular-lymphoma/"},{"id":"mantle-cell-lymphoma","kind":"cancer","name":"Mantle cell lymphoma","route":"/cancers/mantle-cell-lymphoma/"},{"id":"marginal-zone-lymphoma","kind":"cancer","name":"Marginal zone lymphoma","route":"/cancers/marginal-zone-lymphoma/"},{"id":"non-hodgkin-lymphoma","kind":"cancer","name":"Non-Hodgkin lymphoma (all types)","route":"/cancers/non-hodgkin-lymphoma/"}],"drug":[{"id":"epcoritamab","kind":"drug","name":"Epcoritamab","route":"/drugs/epcoritamab/"},{"id":"glofitamab","kind":"drug","name":"Glofitamab","route":"/drugs/glofitamab/"},{"id":"mosunetuzumab","kind":"drug","name":"Mosunetuzumab","route":"/drugs/mosunetuzumab/"},{"id":"obinutuzumab","kind":"drug","name":"Obinutuzumab","route":"/drugs/obinutuzumab/"},{"id":"rituximab","kind":"drug","name":"Rituximab","route":"/drugs/rituximab/"}],"term":[{"id":"antigen-escape","kind":"term","name":"Antigen escape (antigen loss, lineage switch)","route":"/terms/antigen-escape/"},{"id":"lymphoma-bio-antigen-escape","kind":"term","name":"Antigen escape: how a lymphoma loses the thing the drug was aimed at","route":"/terms/lymphoma-bio-antigen-escape/"},{"id":"flow-cytometry","kind":"term","name":"Flow cytometry (immunophenotyping)","route":"/terms/flow-cytometry/"},{"id":"ihc","kind":"term","name":"Immunohistochemistry (IHC)","route":"/terms/ihc/"},{"id":"lymphoma-bio-lineage-antigen-cost","kind":"term","name":"What it costs to aim at a lineage antigen","route":"/terms/lymphoma-bio-lineage-antigen-cost/"}],"target":[{"id":"cd20","kind":"target","name":"CD20","route":"/targets/cd20/"}]}}