Although research into the concordance of EGFR and KRAS mutation status between matched primary and metastatic tumours exists [33], to the authors’ knowledge, no review to date has systematically assessed the currently available data regarding whether metastatic samples are representative of primary tumour samples in patients with aNSCLC in terms of multiple mutations, and included consideration of the mutation testing methodologies employed. The gene discussed is EGFR; the disease is metastatic neoplasm.