The aim of the present study was to simultaneously ascertain and investigate the clinical relevance of all known biomarkers, KRAS exon 2, BRAF V600E, PIK3CA exon 9 and 20 mutational status in conjunction with AREG, EREG mRNA expression, PTEN immunohistochemical protein expression, as well as, skin rash development, in mCRC patients treated with cetuximab containing salvage combination chemotherapy. This evidence concerns the gene KRAS and neoplasm.