However, it is worth mentioning that a significant fraction of HER2+ breast cancer patients, particularly the ones with advanced HER2 gene amplified breast cancer, after treatment with anti-HER2 antibodies eventually relapse or develop progressive disease [100], suggesting that tumors either possess or acquire intrinsic mechanisms of resistance allowing escape from HER2 inhibition mechanisms [100,101,102]. The gene discussed is ERBB2; the disease is breast cancer.