Obesity was associated with BCSM among patients with ER/PR+ and HER2–, and HER2 + tumors, but not among ER– or TNBC patients (ER–: overweight 0.99 [0.64–1.54], obesity 1.03 [0.89–1.20]; TNBC: overweight 1.00 [0.87–1.15], obesity 1.17 [0.92–1.47]). The gene discussed is ERBB2; the disease is obesity due to melanocortin 4 receptor deficiency.