Contrary to the expected results, no significant differences were detected between BiP positivity and tumor stage (n = 543, from 6 studies, I2 = 62%, CI = [0.30–2.47]), tumor grade (n = 692, from seven studies, I2 = 28%, CI = [0.47–1.31]), menopausal status (n = 598, from five studies, I2 = 26%, CI = [0.75–1.85]), ER expression (n = 734, from seven studies, I2 = 0%, CI = [0.62–1.33]), or HER2 expression (n = 837, from nine studies, I2 = 13%, CI = [0.58–1.42]). This evidence concerns the gene ESR1 and neoplasm.