Genetic Testing and Molecular Profiling

As a result of investments in breast cancer research, we know that breast cancer is a series of complex diseases, involving genetic mutations within tumors – changes in the way that genes function.  Analyzing those genetic changes in individual tumors is becoming increasingly important, as well as using the information gained to help make treatment decisions. 

Hormone receptors are measured through testing the tumor HER2, Human Epidermal growth factor Receptor 2 (also called HER2/neu or ErbB2), which is another important growth factor protein receptor involved in the development and growth of breast cancers.  The ErbB2 gene makes the HER2 proteins that are receptors on breast cells.  HER2 receptors play a vital role in regulating cell growth, division, and repair in normal breast cells.  Over expression of these proteins may lead to increases in cell growth and cancer formation.  In approximately 25% of breast cancers, HER2 is overexpressed.  Breast cancers with HER2 gene amplification are called HER2 positive (HER2+).

Other genetic mutations are found in some breast cancers.  Researchers continue to study these mutations to determine exactly how they influence breast cancer growth, and to develop treatments that specifically target the genes responsible.

The importance of hormone receptors and the HER2 gene is explained in greater detail in the Understanding the Diagnosis and Treatment sections.

Next: Lymph Node Involvement.