Type II topoisomerases are essential enzymes, playing important roles in fundamental nuclear processes such as DNA replication and recombination. The TOP2A gene with approximately 30 kb in size encodes a 170 kDa protein. The TOP2A protein is identified as a proliferation marker, expressed in proliferating cells and in numerous human malignant tumours, such as colon, gastric and breast cancer, lymphomas and others. Type II topoisomerases are the targets for anticancer drugs, which can be the topoisomerase II inhibitor therapies like the anthracyclines Doxorubicin and Epirubicin. TOP2A IQFISH pharmDx is developed to detect amplifications and deletions (copy number changes) of the TOP2A gene using fluorescence in situ hybridization (FISH) technique on formalin-fixed, paraffin-embedded human breast cancer tissue specimens. Deletions, as well as the amplification of the TOP2A gene, serve as markers for poor prognosis in high-risk breast cancer patients. TOP2A gene amplification detected by the TOP2A IQFISH pharmDx is further designated as an aid to predict recurrence-free and overall survival in high-risk breast cancer patients treated with adjuvant epirubicin-based chemotherapy.