ESR1 and obesity due to melanocortin 4 receptor deficiency: While in postmenopausal patients obesity increases the risk of estrogen receptor-positive (ER+) BC subtypes, the incidence of triple-negative tumors (that do not express ER, progesterone receptor (PR), or human epidermal growth factor receptor 2 (HER2)) may be enhanced in premenopausal women with obesity [4,5,6,7].