{"entity":{"id":"paper-ren-tnbc-mmr-msi-440-front-oncol-2021","kind":"paper","name":"Mismatch repair deficiency and microsatellite instability in triple-negative breast cancer: a retrospective study of 440 patients","aka":[],"tldr":"Among 440 Chinese women with triple-negative breast cancer, none had high microsatellite instability by PCR and only one had lost a mismatch repair protein, so the tumour-agnostic immunotherapy route through microsatellite instability almost never applies.","summary":"Tissue microarrays from 440 TNBC patients (median age 49, median follow-up 68 months) were stained for MLH1, MSH2, MSH6 and PMS2; 195 were also tested by MSI PCR. All samples were proficient except one with MSH2 loss and intact MSH6; PCR found no MSI-high case, 14 (7.2%) MSI-low and 181 (92.8%) stable. The dMMR sample had low-frequency instability and a possible EPCAM deletion. MMR and MSI status did not correlate with clinicopathological features, PD-1/PD-L1 expression or survival.","asOf":"2026-09-24","links":[{"label":"Ren et al., Front Oncol 2021: mismatch repair and MSI in 440 Chinese TNBC patients","url":"https://doi.org/10.3389/fonc.2021.570623"},{"label":"PubMed","url":"https://pubmed.ncbi.nlm.nih.gov/33747906/"}],"tags":[],"related":["msi-high","dmmr-ihc"],"cancers":["tnbc"],"sections":[],"technologies":["msi-mmr-testing"],"targets":["mmr"],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["msi"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"journal":"Frontiers in Oncology","year":2021,"doi":"10.3389/fonc.2021.570623","pmid":"33747906","authors":"Ren XY, Song Y, Wang J, et al.","paperType":"observational","findings":["dMMR by IHC in 1 of 440 (0.2%); MSI-high by PCR in 0 of 195.","MMR/MSI status unrelated to PD-L1 or survival."],"whatItMeans":"MSI testing has a very low yield in TNBC; TMB and PD-L1 are the immunotherapy biomarkers worth pursuing.","caveats":["Single Chinese centre; tissue microarray cores may miss heterogeneous loss.","PCR performed in fewer than half the cohort."],"changedPractice":false,"participants":440},"route":"/key-papers/paper-ren-tnbc-mmr-msi-440-front-oncol-2021/","neighbours":{"biomarker":[{"id":"dmmr-ihc","kind":"biomarker","name":"dMMR (mismatch repair deficiency by IHC)","route":"/biomarkers/dmmr-ihc/"},{"id":"msi-high","kind":"biomarker","name":"MSI-high (microsatellite instability by PCR or sequencing)","route":"/biomarkers/msi-high/"}],"cancer":[{"id":"tnbc","kind":"cancer","name":"Triple-negative breast cancer (TNBC)","route":"/cancers/tnbc/"}],"technology":[{"id":"msi-mmr-testing","kind":"technology","name":"MSI and mismatch-repair testing","route":"/technologies/msi-mmr-testing/"}],"target":[{"id":"mmr","kind":"target","name":"Mismatch repair proteins (MLH1, MSH2, MSH6, PMS2)","route":"/targets/mmr/"}],"term":[{"id":"msi","kind":"term","name":"Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR)","route":"/terms/msi/"}]}}