Although most of these studies showed an increased risk of death related to obesity, in the modern era of adjuvant anthracyclines and taxanes the association between BMI and disease recurrence and/or breast cancer mortality (BCM) requires further exploration together with an examination of the magnitude of such associations by pathological subtype, that is estrogen receptor (ER)/progesterone receptor (PR)-positive/human epidermal growth factor-2 (HER2)-negative, HER2-positive, triple-negative). The gene discussed is ESR1; the disease is breast cancer.