Kwan et al. evaluated the effects of BMI in a set of 1,676 early-stage tumors where intrinsic subtype was assigned using the PAM50 qRT-PCR assay [11] and found that high obesity (BMI ≥ 35) was associated with decreased expression of ESR1 and increased expression of proliferation genes. The gene discussed is ESR1; the disease is obesity due to melanocortin 4 receptor deficiency.