The Extended RAS Panel detects the presence of 56 specific mutations in RAS genes (KRAS exons 2, 3, and 4 and NRAS exons 2, 3, and 4) in the tumor tissue of patients with mCRC. If the Extended RAS Panel result indicates that a mutation is present in the colorectal cancer tissue, then panitumumab is not recommended. If the Extended RAS Panel does not detect a mutation (presumed to be RAS mutation-negative), then panitumumab may be an appropriate treatment option.