Human breast cancers are heterogeneous tissues comprised of all four cell phenotypes. Primary breast tumors exhibited a similar cellular heterogeneity to normal reduction mammoplasty tissues when examined by flow cytometry using the markers EpCAM, CD24, and CD49f as described in Materials and methods. (a) Representative flow cytometry dot plots of EpCAM and CD49f expression in reduction mammoplasty tissues (RM) and primary human breast tumors of different subtypes. Quantification of flow cytometry tumors (n = 8) classified clinically by expression of ER, PR and Her2 expression. (b) Primary breast cancers demonstrated heterogeneous expression of markers used to characterize cancer cell line xenografts by immunohistochemistry as in Figure 2. Bar = 100 μm.