ERBB2 and breast neoplasm: Distinct combinations of the presence (+) or absence (–) of these receptors permit the categorization of breast tumors into four individual groups, namely ER+/PR+/HER2+; ER+/PR+/HER2–; ER–/PR–/HER2+; and ER–/PR–/HER2–, or triple negative.4 Absence of ER/PR has been strictly defined as less than 1% expression by the most recent American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines.5