Clinicopathologic Analysis of Five Patients with -Mutated Colorectal Cancer in a Single Korean Institute.

: Mutations in RAS/RAF are common in colorectal cancer (CRC) and play a pivotal role in guiding treatment selection. With the recent advent of immunotherapy, microsatellite (MSI) status, tumor mutation burden (TMB), and mutations, particularly those leading to high TMB, have gained importance in CRC. This study aimed to examine the clinicopathological characteristics of patients with CRC with mutations. : We identified mutations in patients with colorectal cancer who had available next-generation sequencing (NGS) results from a single institute in Korea. RAS/RAF status, MSI status, and TMB were evaluated, and based on the TMB results, patients with mutations were classified as having either pathogenic or non-pathogenic mutations. After excluding non-Korean patients, we compared the groups based on the presence of pathogenic mutations. : Five mutations (A456P, P286R, R1111W, R609W, and V922I) were identified. Only A456P and P286R were associated with an exceptionally high TMB, resulting in two patients (1.1%) being categorized as having pathogenic . The -mutant group showed an extremely high TMB and tended to include younger patients. Among the two pathogenic cases, one showed poor histological differentiation, and the tumors were split between the right and left colons (one in each). : CRC with mutations tend to exhibit TMB-high, occur in younger patients, localize to the right colon, and display poor histological differentiation. Given that mutations can serve as indicators for immunotherapy, recognizing these mutations is of clinical importance.