• the size of the tumor,
• other characteristics of the patient's tumor, and
• whether there is cancer in the patient's lymph nodes.

This is not a very precise way to understand how an individual woman's breast cancer will act or how to treat it. Most scientists believe that a more precise way is to learn how specific breast cancer genes work. They hope to find ways to repair or counter the work of these genes.

Genes are pieces of DNA, the molecules inside cells that carry genetic information and pass it from one generation to the next. Most genes are responsible for making specific proteins. Proteins are needed for the body to function properly. By studying genes and the proteins they make, scientists are learning a lot about breast cancer.

Scientists look at breast cancer cells from the tumors of breast cancer patients. With new tools that have been developed, scientists can now look at all of the genes in breast cancer cells. They try to see how genes act in each woman's breast cancer. If there are genes that act the same way in several women's breast cancers, this is called a "pattern." Then scientists try to figure out if the pattern has meaning. For example, did this genetic pattern cause the breast cancer? Are breast cancers with this genetic pattern less aggressive or more aggressive than other breast cancers? These patterns are also called "gene expression profiles" or "gene panels." This just means it is a description of how genes behave in certain breast cancer cells. These gene expression profiles, or molecular profiles, are allowing breast cancers to be grouped in new ways. Some day this type of "gene profiling" will replace the current way doctors describe breast cancer stages. Researchers hope that they will be able to develop different treatments that are targeted to the different subtypes of breast cancer.

Gene expression profiles are different from other types of genetic tests that are used to identify women at a higher risk for developing breast cancer. Genetic tests looking at breast cancer risk are for women not yet diagnosed with breast cancer, while gene expression profiles are for women who have already been diagnosed. Click here to learn more about genetic tests.

This is where breast cancer research and treatment is headed. So it will be more and more important to understand your specific disease characteristics. Your breast tumor contains very important information. And it is important that your breast tissue is preserved and that you have access to it in the future. You should discuss this with your doctor and ask if a tissue bank is available to store your tissue.