Apart from proliferation stimulation, HER2 overexpression also promotes the epithelial to mesenchymal transition of tumor cells, which is accompanied with an enhanced expression of metalloproteinase, causing HER2 shedding and the accumulation of intracellular carboxy-terminal HER2 component p95, a predictive marker for trastuzumab resistance [7], as well as the degradation of extracellular matrix proteins and the concomitant increase in tumor cell migration, which enables rapid invasion [8]. The gene discussed is ERBB2; the disease is neoplasm.