Haematoxylin and eosin (H&E) staining demonstrated that the primary mammary tumours of PyMT-Fib-cKO mice were of a lower grade than tumours from PyMT-Fib-WT mice, and had reduced neoplastic areas in tandem with severely impaired ECM deposition in the stroma (Fig. 3a). Here, FBL is linked to breast cancer.