Consequently, approval for gefitinib administration was expanded in 2011 to include “EGFR mutation-positive inoperable or recurrent non-small-cell lung cancer.” Similarly, the efficacy of cetuximab, an antibody drug for colorectal, head, and neck cancers, was found to be influenced by the presence of KRAS mutations; accordingly, the administration guideline for cetuximab was modified in 2010 and must now consider the presence or absence of KRAS mutations (6), (7). Here, KRAS is linked to malignant tumor of neck.