Adenocarcinomas exhibit activated ERK1/2 in stroma and AKT in epithelia; carcinosarcomas display strong epithelial pERK1/2. (a) pERK1/2 localized in stromal cells of differentiated glandular adenocarcinomas. (b) Mammary carcinosarcomas demonstrated nuclear and cytoplasmic staining for pERK1/2. (c) Carcinosarcoma from gland of NRL-PRL female (hematoxylin and eosin stain). (d) Glandular adenocarcinoma from NRL-PRL female demonstrating nuclear and cytoplasmic staining for pAKT. (e) pAKT localized primarily in the stroma of a squamous adenocarcinoma. (f, g) Carcinosarcomas demonstrated variable levels of pAKT expression. (h) Carcinosarcomas demonstrated significantly higher levels of vimentin mRNA compared to either morphologically normal MECs or more differentiated adenocarcinomas from NRL-PRL females. (i) Carcinosarcomas had similar levels of keratin 8 transcripts compared to adenocarcinomas. (j) Mmp9 mRNA was significantly increased in carcinosarcomas. Transcript levels were measured using qRT-PCR as described in Materials and Methods and represented as mean ± s.e.m. (MECs, N = 3 samples, each containing RNA pooled from 5 mice; carcinosarcomas, N = 4; adenocarcinomas with high pStat5, N = 5). Letters denote significant differences using ANOVA, followed by Newman-Keuls post test (P < 0.05). Original magnification: a, c, 200x; b, d, e, f, g, 400x.