To investigate the in vivo roles of ColXV in mammary tumourigenesis, we crossed Col15a1−/− mice with the MMTV-PyMT model and compared tumour development in the PyMT;Col15a1−/− crosses with the wild-type MMTV-PyMT (PyMT) mice from 4 weeks up to 14 weeks of age. Here, COL15A1 is linked to neoplasm.