BRCA1 and breast neoplasm: An example of such studies was carried out by Lim et al. in BRCA1 mutation-associated breast tumors, where the authors prospectively isolated distinct subpopulations of normal and tumorigenic epithelial cells from BRCA1 mutation heterozygous individuals and found that luminal progenitors were highly represented in BRCA1 mutation-associated breast tumors, more than the stem cell population [21].