TP53 and squamous cell carcinoma: Three (23.1%) specimens with a T790M loss had additional mutations, including one with an EGFR and AKT1 amplification and a PDGFR mutation (p.D1033V), one had a CTNNB1 (p.D32Y) and a BRAF (p.V600E) mutation, and the other exhibited transformation to squamous cell carcinoma and contained a TP53 mutation (p.V73fs).