If you are in Arm C (which as discussed above, does not include colorectal cancer patients with a KRAS mutation), a leftover sample of tumor tissue will be tested for the KRAS mutation. If no leftover tumor tissue from an earlier procedure is available, and if your KRAS status is unknown, you will have a needle biopsy of a tumor performed. The tissue will be tested for the KRAS mutation. This procedure will be done on an appropriate tumor area that is able to be biopsied, and it may or may not be the liver tumor. This will be the doctor's decision.