The differences between these include the following: enriched expression of some genes (eg PIK3CA, ADH7 and SPRR3) in the SCC keratin—high compared with the SCC keratin—low cluster, more frequent CNVs, including common EGFR amplification in SCCs, a high number of aberrations in tumour‐suppressor genes related to TGF‐β pathway in adenocarcinomas including SMAD4 and TGFBR2 deletions, and increased DNA methylation in adenocarcinomas.65 This evidence concerns the gene PIK3CA and adenocarcinoma.