ERBB2 and atrial fibrillation: Her medical history consists of hypertension, atrial fibrillation, pacemaker placement, and left-sided mastectomy 4.5 years ago for a pT1cN3M0 oestrogen receptor (ER) 60% positive, progesterone receptor (PR) 90% positive, and Human Epidermal Growth Factor Receptor 2 (HER2) negative invasive lobular carcinoma.