MSH6 and neoplasm: In addition, a retrospective analysis of MSI-h tumours found that TMB varies depending on whether MutS or MutL-related proteins had been lost, with MSH2/MSH6 deficient tumours having ∼46 mutations per megabase (mut/Mb) whilst MLH1/PMS2 deficient tumours had ∼25 mut/Mb [13].