ERBB2 and breast cancer: Topoisomerase II alpha [TOP2A] is one of the 2 types of Type II topoisomerases.[73,74] High expression of TOP2A is detected in several types of cancer, and TOP2A has been recognized as a cancer target in clinical application.[75–77] It is well known that the HER2 gene has a well-established biological and clinical role in BC, and the HER2 amplicon on chromosome 17 harbors a great quality of genes involved in BC pathophysiology.