Causes of mismatch repair (MMR) deficiency
| MMR-deficient tumours | Subclonal loss N (%) | ||
| Resections N (%) | Biopsies N (%) | Resections N (%) | |
| MLH1 promoter hypermethylation | 30 (40.5) | 2 (66.7) | 3 (42.9) |
| Two somatic hits | 10 (13.5) | 0 | 1 (14.3) |
| Lynch syndrome | 20 (27.0) | 0 | 0 |
| MLH1 variant | 6 | ||
| MSH2 variant | 7 | ||
| PMS2 variant | 2 | ||
| MSH6 variant | 5 | ||
| MMR variants identified in tumour, normal tissue not available, but high variant allele frequency | 6 (8.1) | 0 | 0 |
| MMR deficiency molecularly unexplained (no or only one somatic hit identified) | 8 (10.8) | 1 (33.3) | 3 (42.9) |
| Total | 74 | 3 | 7 |