What does "her 2 neu" mean?

Tumor Marker: Her 2/neu is a cell membrane protein that is overexpressed in as many as 30% of breast cancer patients. Those patients that overexpress this marker tend to have more aggressive cancers, although these patients are preferentially able to be treated with a chemotherapy drug that targets these tumors called herceptin (trastuzumab).

Breast cancer gene: Her2 (human epidermal growth factor receptor 2) also known as neu, erbb-2, cd340 (cluster of differentiation 340) or p185 is a protein that in humans is encoded by the erbb2 gene. Her2 is a member of the epidermal growth factor receptor (egfr/erbb) family. Amplification or over-expression of this gene has been shown to play an important role in the pathogenesis and progression of certain aggressiv.

Genetic marker. : It is a genetic marker that can be found several kinds of cancer including breast, stomach, and uterine cancer. If the cancer is positive for this marker or exhibits over-amplification of this gene, it can be associated with a more aggressive course.