PGR and breast cancer: TNBC is defined as cases where cancer cells lack joint hormone receptor (HR; estrogen [ER] and progesterone receptors [PR]) and display low levels of human epidermal growth factor receptor (HER2).15 Black women are approximately twice as likely to be diagnosed with TNBC than white women.16 TNBC is associated with larger and higher-grade carcinomas at diagnosis and cannot be treated by endocrine-based treatments,17 resulting in higher rates of 5-year cancer-related mortality compared with other types of breast cancer (40% vs. 20%).18