ESR1 and breast cancer: Certain anatomopathological features can help in the identification of breast tumors with mutations in the BRCA1 gene (cancers with a high degree of differentiation, increased mitotic index, lymphocytic infiltrate without HER2 receptor and without estrogen receptors); women carrying BRCA1 gene mutations, those with ER (-) or those with a history of breast cancer without estrogen receptors have an increased risk of developing a tumor ER (-) [3].