In contrast to myoepithelial staining, Ki67 expression, which indicates an increase in proliferation, was expressed most abundantly in the invasive regions of tissues derived from the C57BL/6J MMTV-PyMT mice (Fig 3 and Table 1), as expected due to the high rate of growth of invasive tumour upon palpation in this model [24]. The gene discussed is MKI67; the disease is neoplasm.