ESR1 and obesity due to melanocortin 4 receptor deficiency: This pattern of association is essentially similar to one reported for obesity, per se, which correlates with worse prognosis in BC patients bearing luminal tumors, while no such association was found in non-luminal tumors [13,14,26,27], and further supports the contribution of the enzyme to BC-promoting effects of obesity through Mφ-mediated upregulation of ER.