Intra-tumoral clonal heterogeneity, co-existence of the two alterations in the same tumor cells, very rapid acquisition of the co-alteration right after initiating TKI-treatment, or a combination of these circumstances have been envisioned as possible causes of EGFR/ALK co-alteration in NSCLC [42,91,128]. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.