Since PyMT+/− mice developed luminal CK8+ tumors with enhanced Rank expression compared with non-tumorigenic mammary epithelia adenocarcinomas [11, 17] and Rank overexpression led to a reduction in the CD61+ luminal populations [18], we hypothesized that tumors might originate from these luminal populations, explaining the attenuation of tumorigenesis observed in PyMT+/−Rank+/tg double transgenic mice [18]. This evidence concerns the gene KRT8 and adenocarcinoma.