ESR1 and breast carcinoma: Basal cytokeratin (CK5/14/17)-positive tumors represent about 10% of sporadic breast carcinomas and are almost exclusively ER-negative, poorly differentiated, and associated with epidermal growth factor receptor (EGFR), p53, vimentin, and c-kit immunopositivity and Bcl-2 negativity [11,12,14-16,19-21].