ERBB2 and breast cancer: Chromosome17 (Chr17) is the second most gene-dense chromosome in the human genome [1], containing many genes central to breast cancer development and progression, including oncogenes (HER2, TOP2A, STARD3, TAU), tumor suppressor genes (TP53, BRCA1, HIC-1) and DNA double-strand break repair genes (RDM1) [2–7].