In contrast, there were differences in the gene mutation profiles and protein expression patterns in the SCLC and NSCLC components of the CSCLC (groups 2–4): Divergent genetic changes were noted in the SCLC and NSCLC component in two cases (EGFR mutation only in the AD component of case 2 in Group 2, and K-ras mutation only in the SCLC component of case 2 in Group 3). Here, KRAS is linked to small cell lung carcinoma.