Oncologists and other cancer specialists look at whether breast cancer cells have certain characteristics that can predict aggressive growth. Pathology results from the biopsy will determine:

• Whether the cancer has receptors for the hormones estrogen and progesterone. You'll hear the doctor use the terms ER-positive or ER-negative, which means the tumor tested positive or negative for an abundance of estrogen receptors.
• The amount of a protein called HER-2 produced by cancer cells. A HER-2 positive tumor is considered to be more aggressive, but it also means your family member can take Herceptin, a new drug that treats HER-2 positive tumors with excellent success.

Information about hormonal receptor status and HER-2 status can help the doctor recommend an individualized treatment plan that will offer the best chance of curing or controlling the cancer.