Some cancer types and their CTCs, however, may not express EpCAM.14 Also, CTCs are capable of transitioning from an epithelial to mesenchymal phenotype, rendering the cells more aggressive and invasive.15–19 Along this transition, CTCs down-regulate EpCAM, which implies that an affinity-based capture method may miss the most clinically relevant and aggressive CTCs. The gene discussed is EPCAM; the disease is cancer.