ERBB2 and obesity due to melanocortin 4 receptor deficiency: However, unlike the observation of higher BMI and shorter breastfeeding duration in triple-negative patients among Western, especially African American, women [18, 19, 28, 29], we found lower frequencies of obesity and breastfeeding among HR− (HER2-enriched and triple-negative) than luminal A-like tumors, which may be reflective of population/ethnic differences.