CYP19A1 and obesity due to melanocortin 4 receptor deficiency: These paradoxical observations may be explained by lower efficiency of anticancer drugs, particularly aromatase inhibitors, in obese patients and by better compliance to treatment among normal weight patients [37]; still, further studies are needed to resolve the paradox as to why obesity may be related to an increased risk of less aggressive breast tumors, while at the same time being associated with worse prognosis irrespective of the tumor subtype.