ESR1 and breast cancer: That MUC6 positivity was linked to advanced stage in colorectal adenocarcinoma and to high Bloom‐Richardson‐Elston grade, nodal metastasis and molecular features that are related to aggressive tumor phenotype (ER negative, PR negative, and HER2 positive) in breast cancers of no special type demonstrates that high MUC6 expression can be linked to a more aggressive tumor behavior.