IHC loss and germline path_MMR detection rates in CRC and EC index samples tested
| Colorectal | Number tested | IHC loss | % | Number tested germline | Germline path_MMR | % Germline path_MMR | |
| MLH1 and PMS2 loss | 2204 | 171 | 7.8 | 104 | 40‡ | 38.5% | 37 MLH1, 3 PMS2 |
| MLH1 loss alone | 2204 | 51 | 2.3 | 33 | 24‡ | 72.7% | 24 MLH1 |
| PMS2 loss alone | 2204 | 25 | 1.1 | 21 | 14 | 66.7% | 14 PMS2 |
| MSH2 and MSH6 loss | 2204 | 81 | 3.7 | 76 | 54 | 71.0% | 48 MSH2, 6 MSH6 |
| MSH2 loss alone | 2204 | 45 | 2.0 | 32 | 8 | 25.0% | 8 MSH2 |
| MSH6 loss alone | 2204 | 41 | 1.9 | 30 | 15 | 50.0% | 15 MSH6 |
| Either MSH2 or MSH6 | 2204 | 175 | 7.9 | 140 | 77 | 55.0% | 56 MSH2, 21MSH6 |
| Any loss | 2204 | 422 | 19.1 | 298 | 155 | 52.0% | |
| Tested (n) | Positive (n) | ||||||
| MLH1 loss hypermethylation | 163 | 67* | 41.1 | 23 | 1 | 4.3% | MLH1 |
| MLH1 loss BRAF c.1799T>A | 170 | 45 | 26.5 | 11 | 3 | 27.3% | |
| No loss | 1782 | 0 | 0.0 | 176 | 18† | 10.2% | 4 MLH1, 7 MSH2, 3 MSH6, 4 PMS2 |
| EndometrialC | |||||||
| MLH1 and PMS2 loss | 739 | 108 | 14.6% | 43 | 2† | 4.6% | 2 MLH1 |
| MLH1 loss alone | 739 | 4 | 0.5 | 4 | 0 | 0% | |
| PMS2 loss alone | 739 | 7 | 0.95 | 5 | 5 | 100.0% | 5 PMS2 |
| MSH2 and MSH6 loss | 739 | 32 | 4.3 | 29 | 16 | 55.2% | 12 MSH2, 6 MSH6 |
| MSH2 loss alone | 739 | 2 | 0.3 | 2 | 1 | 50% | 1 MSH2 |
| MSH6 loss alone | 739 | 30 | 4.1 | 30 | 18 | 60.0% | 18 MSH6 |
| Either MSH2 or MSH6 | 739 | 64 | 8.7 | 61 | 37 | 60.7% | 24 MSH6, 13 MSH2 |
| Any loss | 739 | 183 | 24.8 | 113 | 44 | 38.9% | |
| Tested (n) | Positive (n) | ||||||
| MLH1 loss hypermethylation | 109 | 95 | 87.2 | 32 | 0 | 0.0% | |
| MLH1 loss BRAF c.1799T>A | Not systematically tested | ||||||
| No loss | 556 | – | 0.0 | 120 | 1 | 0.8% | 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.