EPCAM and neoplasm: While CTC analyses have typically relied upon selection of epithelial-phenotype CTCs via EpCAM, CK, or other epithelial markers, mesenchymal- and mixed epithelial/mesenchymal-phenotype CTCs are, a priori, more consistent with the characteristics of metastatic tumor cells, including enhanced motility, invasiveness, and self-renewal [42]; indeed, data from several recent studies across multiple tumor types have suggested that mesenchymal- or mixed E/M-phenotype CTCs may be of greater prognostic and/or predictive value than their epithelial-phenotype counterparts [24–27].