"TARGETED_REGION" is not a mutation type, but an annotation. It means that this genomic region was successfully covered by targeted sequencing for this sample and no mutations were found in it (wild-type status). This annotation allows us to distinguish between regions that have been tested and found to be “clean” and regions that have not been sequenced at all in this sample. This is critical for the correct calculation of mutation frequency in the cohort, as only those samples where the gene has actually been analysed should be included in the denominator.