In contrast, Yu et al.14 reported elevated protein levels of Mdm2 (38%) and Mdmx (65%), and low-level Mdmx gene amplification (56.5% identified by fluorescence in situ hybridization (FISH)) in an apparently wt p53 context (as suggested by an absence of allelic loss and no increased protein detection) in primary breast cancers (BrCas). This evidence concerns the gene MDM4 and breast cancer.