The SOX9+LGR5+ signature is stronger in tumors characterized by high copy number (copy-number-high) alterations (Wilcoxon text, P value 6.72 × 10−13), typical of serous endometrial adenocarcinomas and linked with a worse prognosis (Supplementary Table 3). Here, SOX9 is linked to endometrial serous adenocarcinoma.