STAT5A and breast cancer: The STAT family was proposed as a biomarker or immune checkpoint inhibitor for prognosis prediction or therapy in various types of solid tumors, including STAT3 and STAT5A in breast cancer (Wu et al., 2017); STAT3, STAT5A, and STAT6 in lung cancer (Pastuszak-Lewandoska et al., 2017); and STAT3 and STAT5A in prostate cancer (Mohanty et al., 2017).