With regard to the origin of these ER+BRCA1-related breast cancers, Lim et al observed the expansion of a committed luminal progenitor population, containing ER+ and ER− cells, in preneoplastic tissues of BRCA1 mutation carriers and proposed the luminal progenitor cells as the cell of origin for BRCA1-associated cancers (11). This evidence concerns the gene BRCA1 and breast carcinoma.