EGFR and neoplasm: Notwithstanding this, it is important to note that tumours are indeed heterogenous in nature and both inter- and intra-tumour heterogeneity could also contribute to the variability in the reported expression of EGFR and the lack of association with response to EGFR therapies, as well as discordance between the expression of EGFR in the primary tumour and its metastatic lesions [167].