Most CEs are asymptomatic, occurs during anti-HER2 treatment and further accumulate from the 6th to the 12th month of treatment, thus cardiac monitoring in this period should be followed according to guidelines, especially for patients with one or more of the following risk factors: pre-treatment LVEF < 55%, BMI > 30 kg/m2, high cumulative anthracycline exposure and DM. Here, ERBB2 is linked to cat-eye syndrome.