Fgfr2ΔE18 variants rapidly induced mammary tumours regardless of Cdh1 mutation status (Fig. 2c,d and Extended Data Fig. 6d–g), and progressive truncation of Fgfr2-E18 gradually decreased tumour onset (Fig. 2e and Extended Data Figs. 6h and 7a,b). Here, CDH1 is linked to breast cancer.