Consistent with our findings in tumour-derived cell lines, MMTV-Metmt;Trp53fl/+;Cre and Trp53fl/+;Cre mammary tumours with spindloid pathology showed stronger immunohistochemical staining for FGFR1 when compared to tumours with non-spindloid pathologies (Fig. 3c). This evidence concerns the gene FGFR1 and breast cancer.