In addition, in the PyMT;Col15a1−/− tumour stroma, the collagen fibrils were slightly, although not statistically significantly, smaller in diameter and were also more variable in size than fibrils in the control samples (Figure 3D–F; for PyMT, M (mean fibril diameter) is 46.1 ± 7.9 nm and SD% (standard deviation of fibril diameter in %) is 17.2 ± 1.8%; for PyMT;Col15a1−/− M is 42.2 ± 8.4 nm and SD% is 19.9 ± 1.2%); t-test for M, p = 0.09 and for (SD%) p = 0.012). Here, COL15A1 is linked to neoplasm.