Fig. 7. (A) Mutant mice develop mammary tumors early in life. (a) A whole-mount image reveals multiple nodules (arrows) in the mutant gland. (b) Virgin mutant transplants with focal ductal hyperplasia containing papillary structures (arrow). (c) Mutant glands after one pregnancy showed intra-luminal focal hyperplasia. Note the ductal epithelial cells contain multi-layers and protrude into the lumen (arrows). (d,e) Mutant gland after one pregnancy with dysplastic changes (d) and pleomorphic nuclei and mitotic figures (arrow in e). (f) Mutant gland with squamous epithelium and keratinous debris within (arrows). (g,h) Tumors from multiparous mutant mammary glands show various histological features, ranging from well differentiated fibroadenoma (g) to pleomorphic adenocarcinoma (h). Scale bar: b, 80 µm; c, 160 µm; d,f,g,h, 80 µm; e, 16 µm. (B) Up-regulated cytokeratin 5 and 6 expressions in the mutant mammary tissue transplants. Cytokeratin 5 (left panels) and cytokeratin 6 (right panels) immuno-staining (in red) of normal virgin (a,b), hyperplastic areas of mutant virgin (c,d) and term glands (e,f). All sections were counter-stained with ß-catenin antibody (in green). Cytokeratin 5 expression is low in myoepithelial cells of normal glands, and is upregulated in hyperplastic areas (arrow in c). Cytokeratin 6 is absent in normal alveoli and is expressed only in epithelial cells that protrude into the lumen of hyperplasic areas (arrows in d). Broader ranges of cytokeratin 5 and 6 expressions can be detected in the term mutant glands (e,f). Bar for a,b,e,f, 80 µm; c,d, 250 µm. (C) Tumor incidence of Pten^loxp/loxp;MMTVCre^+/– (n=37) and Pten^loxp/loxp (n=21) females.