In several cancers such as prostate, non‐small‐cell lung cancers, cervical cancers, renal cell carcinoma, and glioblastoma, activation of STAT3 or STAT5 is associated with a worse prognosis; conversely, STAT3 is associated with favorable prognosis in breast cancer and in some studies in colorectal cancer and head and neck squamous cell carcinoma (Thomas et al., 2015). Here, STAT3 is linked to breast cancer.