ERBB2 and breast cancer: Besides genes known to be involved in the development and progression of breast cancer, such as BRCA1 at 17q21 and ERBB2 at 17q12, the presence of other breast cancer associated genes, both tumor suppressors and oncogenes, have been proposed in the long arm of chromosome 17 on the basis of loss of heterozygosity, allelic imbalance, and comparative genomic hybridization studies [5-9].