TTF1 and neoplasm: In addition, patients whose tumour exhibited no expression of NKX2‐1/TTF‐1 exon 1 had significantly shorter median OS (log‐rank test, p = 0.0306; Breslow–Wilcoxon test, p = 0.0032); however, these differences were barely significant compared to TTF‐1 protein expression (Figure 5D).