Evidence suggests that rhein and its derivatives have anticancer activities in various malignancies, such as breast cancer (BC) overexpressing HER2/neu (MCF7/HER2), triple-negative BC (MDA-MB-231 and 4T1 TNBC cell lines), oral cancer (OC) (YD-10B and Ca9-22 cell lines), gastric cancer (HGC-27), liver cancer (HepG2 and Huh7), colorectal cancer (CRC), ovarian cancer (A2780, SKOV3, SKOV3-PM), and non-small-cell lung cancer [10,11,18,19,51,52,53,54,55,56]. This evidence concerns the gene ERBB2 and breast cancer.