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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.
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.
MSI testing has a very low yield in TNBC; TMB and PD-L1 are the immunotherapy biomarkers worth pursuing.
Shares Mismatch repair proteins (MLH1, MSH2, MSH6, PMS2), dMMR (mismatch repair deficiency by IHC), MSI-high (microsatellite instability by PCR or sequencing), Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR).
Shares Mismatch repair proteins (MLH1, MSH2, MSH6, PMS2), MSI-high (microsatellite instability by PCR or sequencing), Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR), Triple-negative breast cancer (TNBC).
Shares MSI and mismatch-repair testing, Mismatch repair proteins (MLH1, MSH2, MSH6, PMS2), dMMR (mismatch repair deficiency by IHC), Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR).
Shares MSI and mismatch-repair testing, Mismatch repair proteins (MLH1, MSH2, MSH6, PMS2), MSI-high (microsatellite instability by PCR or sequencing), Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR).
Shares MSI and mismatch-repair testing, dMMR (mismatch repair deficiency by IHC), Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR), Triple-negative breast cancer (TNBC).
Shares Mismatch repair proteins (MLH1, MSH2, MSH6, PMS2), MSI-high (microsatellite instability by PCR or sequencing), Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR).
Shares Mismatch repair proteins (MLH1, MSH2, MSH6, PMS2), Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR).
Shares dMMR (mismatch repair deficiency by IHC), MSI-high (microsatellite instability by PCR or sequencing), Triple-negative breast cancer (TNBC).