PIK3CA and breast carcinoma: Given that the MSigDB “HALLMARK_PI3K_AKT_mTOR_SIGNALING” signature used in our study also encompasses mTORC1-related processes, in line with a strong correlation with the separate hallmark mTORC1 signature, our findings support a previous study reporting a negative relationship between the presence of a PIK3CA mutation and mTORC1 signaling in ER-positive/HER2-negative breast cancers [38].