ERBB2 and breast neoplasm: Among the genes that are located in this region and have been reported to be amplified in breast cancers, topoisomerase IIα (TOP2A), a gene coding for the enzyme targeted by anthracyclines, is located 2 Mb from HER2. TOP2A amplification might be linked to the sensitivity to anthracyclines observed in HER2-positive breast tumors [6-18].