Clustering of array CGH data set. The length of each horizontal dendrogram arm indicates the degree of correlation between the various specimens, ranging from 0% to 100% correlation. The shorter the dendrogram arm, the greater the degree of correlation. A, unsupervised hierarchical clustering analysis of copy number alterations on the whole sample set (18 pairs of primary tumors and corresponding xenografts). B, hierarchical clustering analysis, including the metastasis-derived xenografts HBCx-13B and HBCx-12B (indicated with circles). CGH, comparative genomic hybridization, HBC, human breast cancer, HBC-n, HBC primary tumor n, HBCx-n, HBC xenograft tumor n, HER2+, human epidermal growth factor receptor 2 positive. Red, luminal tumors; black, triple-negative tumors; green, HER2+ tumors.