ALDH1A1 and breast cancer: In a later study involving 130 patients with metastatic BC including 68.5% of ER + vc BCs, CTCs positive for ALDH1+ and marked with both cytokeratins (CK8, 18, and 19, epithelial markers) and TWIST1 (a mesenchymal marker) were associated with lung metastasis as well as reductions in OS and progression-free survival [258].