HER‐2 gene amplification can be acquired as breast cancer progresses. - Meng,S.; Tripathy,D.; Shete,S.; Ashfaq,R.; Haley,B.; Perkins,S.; Beitsch,P.; Khan,A.; Euhus,D.; Osborne,C.; Frenkel,E.; Hoover,S.; et al. (Proc Natl Acad Sci USA, 2004)