Benchmarking mismatch repair testing for patients with cancer receiving immunotherapy (vol 42, 323, 2024)

Immunohistochemistry (IHC) is currently the first-line test for mismatch repair deficiency (MMR-D). Bou Farhat et al. show that mismatch repair (MMR) mutation signature by next-generation sequencing is a highly sensitive assay capable of detecting MMR-D cases that are missed in 1% and 5% of patients with MMR-D colorectal cancer (CRC) and endometrial cancer (EC), respectively. Patients with MMR-D tumors missed by IHC have similar clinical outcomes to patients with MMR-D by both IHC and mutation signature.