ESR1 and breast carcinoma: In line with previous findings from us and others [13, 24], female WT mice developed M/D-driven mammary carcinomas expressing estrogen receptor 1 (ESR1, best known as ER) and progesterone receptor (PGR, best known as PR), but not vimentin (VIM)—de facto exhibiting a luminal phenotype—with complete penetrance and a median latency of 89 days from the 1st DMBA gavage (Fig. 1B, C).