RARA and breast cancer: Indeed, recent studies using different techniques, such as comparative genomic hybridization (CGH) [17,18], multiplex ligation-dependent probe amplification (MLPA) [19], single nucleotide polymorphism arrays (SNP arrays) [15], or FISH using alternative chromosome 17 reference genes (RARA, TP53, SMS) [20] suggested that true chromosome 17 polysomy is a rare event in breast cancer.