Gene expression in mammary tumor evolution in MMTV-Wnt-1 transgenic mice. (a) Dendrogram of 35 samples analyzed by average linkage hierarchical clustering analysis, using 3,359 genes selected for high variability across all samples. 15k arrays were used. (b) Immunohistochemical staining for c-Kit in the indicated tissue sections. A 20× objective was used. MMTV, mouse mammary tumor virus; VMG, virgin mammary glands from nontransgenic mice; WntT, mammary tumors from MMTV-Wnt-1 transgenic mice; WntH, hyperplastic mammary glands from MMTV-Wnt-1 transgenic mice.