EGFR and colorectal carcinoma: Right-sided tumours are less prevalent and associated with a poorer prognosis than left-sided tumours.14–17 Right-sided tumours are also more frequently associated with mutations in BRAF, TGFβR2 and PI3KCA. 18,19 In contrast, amplification of EGFR and HER2, overexpression of EGFR ligands and chromosomal instability are more common in left- than right-sided tumours.18–20 According to the CRC Subtyping Consortium, right-sided tumours are more likely to be consensus molecular subtype 1 (CMS1), while left-sided tumours are predominantly CMS2.21