Histological sections of mammary tumors stained with H and E or ki-67 antibody. A. Invasion was identified based on growth patterns such as glandular infiltration into surrounding skeletal muscle fibers (arrow) in tumors from PyMT mice negative for mCAT. Invasive foci were scored from 0 (none) to 3 (multiple invasive fronts). B. Low grade, encapsulated adenomas (closed arrow head) were more common in PyMT mice expressing mCAT. C. Ki-67 staining of PyMT primary tumor cells negative for mCAT showed a labeling percent of 56. D. Ki-67 staining of PyMT primary tumor cells positive for mCAT showed a labeling percent of 21. The difference in ki-67 labeling between mCAT positive and mCAT negative PyMT primary tumor cells was significant at p ≤ 0.05.