The clinical significance of most of the co-occurring alterations at the time of primary diagnosis remains to be investigated, although for some co-occurring alterations it is already well established, such as, for example, the co-occurrence of EGFR and PIK3CA mutations, which is observed in 9.0–12.4% of advanced NSCLC adenocarcinomas [61]. This evidence concerns the gene PIK3CA and adenocarcinoma.