ERBB2 and metastatic malignant neoplasm in the lymph nodes: Among the patients who received chemotherapy and endocrine therapy, the non-metformin diabetic group had decreased DFS (HR 2.14; 95 % CI 1.14 to 4.04) compared with the metformin group, after adjusting for age, BMI, tumor size, lymph node metastasis, ER, PR and HER2.