MKI67 and breast cancer: Several new membrane proteins and prognostic markers have been reported to regulate stemness in specific subtypes of breast cancer, such as protein C receptor (PROCR) [13], tetraspanin 8 (TSPAN8) [14], tumor endothelial marker 8 (TEM8) [15], epsilon sarcoglycan (SGCE) [16], and Ki-67 [17].