Such findings led to a recent guideline update from the American Society of Clinical Oncology supporting omission of sentinel lymph node biopsy for post-menopausal women age 50 years or older with clinical T1, grade 1–2, HR+ HER2- unifocal invasive ductal carcinoma with a negative pre-operative axillary ultrasound [44]. Here, ERBB2 is linked to invasive ductal breast carcinoma.