ALDH1A1 and metastatic neoplasm: Furthermore, PIK3CA and ALDH1 positive CTCs were found to be significantly more frequent in patients with a chemo-naïve or progressive metastatic disease compared to M0 and non-progressive M1 patients (PIK3CA: p = 0.010; ALDH1: chemo-naïve: p = 0.003; progress: 0.017), whereas AKT2 positive CTCs were found in all groups (Supplementary Figure 1).