Table 3

IHC loss and germline path_MMR detection rates in CRC and EC index samples tested

ColorectalNumber testedIHC loss%Number tested germlineGermline path_MMR% Germline path_MMR
MLH1 and PMS2 loss22041717.810440‡38.5%37 MLH1, 3 PMS2
MLH1 loss alone2204512.33324‡72.7%24 MLH1
PMS2 loss alone2204251.1211466.7%14 PMS2
MSH2 and MSH6 loss2204813.7765471.0%48 MSH2, 6 MSH6
MSH2 loss alone2204452.032825.0%8 MSH2
MSH6 loss alone2204411.9301550.0%15 MSH6
Either MSH2 or MSH622041757.91407755.0%56 MSH2, 21MSH6
Any loss220442219.129815552.0%
Tested (n)Positive (n)
MLH1 loss hypermethylation16367*41.12314.3%MLH1
MLH1 loss BRAF c.1799T>A1704526.511327.3%
No loss178200.017618†10.2%4 MLH1, 7 MSH2, 3 MSH6, 4 PMS2
EndometrialC
MLH1 and PMS2 loss73910814.6%432†4.6%2 MLH1
MLH1 loss alone73940.5400%
PMS2 loss alone73970.9555100.0%5 PMS2
MSH2 and MSH6 loss739324.3291655.2%12 MSH2, 6 MSH6
MSH2 loss alone73920.32150%1 MSH2
MSH6 loss alone739304.1301860.0%18 MSH6
Either MSH2 or MSH6739648.7613760.7%24 MSH6, 13 MSH2
Any loss73918324.81134438.9%
Tested (n)Positive (n)
MLH1 loss hypermethylation1099587.23200.0%
MLH1 loss BRAF c.1799T>ANot systematically tested
No loss5560.012010.8%1 MSH6
  • *One patient with CRC had germline MLH1 methylation, #13/74 (17.6%) Amsterdam criteria, 5/102 (4.9%) non-Amsterdam.

  • †This rose to 2/15 unmethylated samples.

  • ‡This rose to 63/114 (55.3%) of unmethylated samples.

  • CRC, colorectal cancer; EC, endometrial cancer; IHC, immunohistochemistry; MMR, mismatch repair; path_, pathogenic variant.