ESR1 and breast carcinoma: Furthermore, one study demonstrated that the favourable effect of CD8+ CTLs was only limited to ER negative, high histological grade breast cancers [27], whereas another recent publication reported that intratumoral CD8+ CTLs only had statistically significant and independent association with better prognosis in triple-negative breast cancer (ER negative, progesterone receptor [PR] negative, HER-2 negative), especially in core basal phenotype breast cancer [ER negative, PR negative, HER-2 negative, epidermal growth factor receptor positive (EGFR) or cytokeratin (CK) 5/6 positive] [28].