In our case, BRAF V600E was not expressed in the primary tumour, and rather than assuming that the slight simultaneous cells with BRAF V600E and EGFR ex19 deletion, metastasized to only one location, it is more consistent to assume that only one of the multiple lung tumours acquired resistance, given that the S6 tumour shrank once and then regressed. The gene discussed is EGFR; the disease is neoplasm.