Endoscopic features of deficient mismatch repair/microsatellite instability‐high and BRAF‐mutated colorectal cancer

AbstractObjectiveRecent advancements in genome analyses, including the BRAF gene and mismatch repair (MMR) gene/microsatellite instability (MSI), have revealed the biological diversity of colorectal cancer (CRC). BRAF‐mutated CRC has a poor prognosis; however, cases exhibiting deficient MMR (dMMR)/MSI‐high (MSI‐H) and BRAF gene mutations have demonstrated significant prognostic improvement following recent immune checkpoint inhibitor therapy. Therefore, the diagnosis of these subtypes is important. This study aimed to identify the endoscopic features of dMMR/MSI‐high and BRAF‐mutated CRCs.MethodsA retrospective analysis was conducted on 292 CRC cases. Clinicopathological findings, focusing on dMMR/MSI‐H and BRAF‐mutated subtypes, were determined. Endoscopic images were analyzed for the presence of yellow slough. Surface material characteristics were assessed through a histopathological evaluation.ResultsOf the 256 cases analyzed, 27 were dMMR/MSI‐H CRC, including 12 BRAF‐mutant cases. Yellow slough was observed in 83.3% of dMMR/MSI‐H and BRAF‐mutated CRCs, compared with 13.3% dMMR/MSI‐H and BRAF wild‐type CRCs and 1.3% pMMR/MSS and BRAF wild‐type CRCs. Histological examination showed a correlation of yellow slough with coagulative necrosis and thicker surface layers in dMMR/MSI‐high and BRAF‐mutated CRCs.ConclusionYellow slough on endoscopy may help identify dMMR/MSI‐H‐ and BRAF‐mutated CRC and allow the initiation of appropriate molecular testing and immunotherapy