The relationship between obesity and BC is already established due to the complications related to surgery, radiation, and chemotherapy, with worst disease-free survival (DFS) and overall survival (OS), and an increased risk for local recurrence in female obese patients compared with their normal-weight counterparts [86] and the increased risk to develop estrogen receptor (ER)-positive BC in postmenopausal women [87,88]. Here, ESR1 is linked to obesity due to melanocortin 4 receptor deficiency.