This grouping of subtypes, based on distribution trends, is consistent with the distinct proliferative behaviors of breast-cancer subtypes as described in Prat and Perou (2011): although similar in some aspects Luminal subtypes are distinguished by the more proliferative aspect of Luminal B; Basal and Her2 subtypes are also considered as aggressive tumors in contrast to Luminal A and Normal-like; Claudin-low subtypes have mixed behaviors depending on conditions but are usually described as lowly proliferative in vivo. This evidence concerns the gene ERBB2 and breast cancer.