ESR1 and breast cancer: American Society of Clinical Oncology (ASCO)/ College of American Pathologists (CAP) defines TNBC as those breast cancers which shows < 1% estrogen receptor (ER)/ progesterone receptor (PR) expression by immunohistochemistry (IHC) and either 0–1+ Her2neu by IHC or 2+ with negative fluorescent insitu hybridization (FISH) [3–5].