Moreover, calculation of the Ki67 proliferation index (i.e., the percentage of Ki67 stained nuclei relative to all nuclei in the primary tumor) showed that, in marked contrast to the index at 1 w p.i., Py230 primary tumors were more proliferative than 4T1 primary tumors by 3 w p.i. (Figure 2), supporting the earlier finding that Py230 tumors are able to catch up with 4T1 tumor growth. Here, MKI67 is linked to neoplasm.