ERBB2 and breast cancer: However, approximately 10.8% to 14.3% HER-2-positive early BC patients develop brain metastasis with an overall survival of less than 2 years.15 Among factors elucidated by Maurer et al,15 our patient had tumor size >2 cm and age <40 years as risk factors for brain metastasis in early HER-2-positive BC patients.