< Back

Breast Cancer Terminology

Aromatase Inhibitor (uh-ROH-muh-tayz in-HIH-bih-ter):

A drug that prevents the formation of estradiol, a female hormone, by interfering with an aromatase enzyme. Aromatase inhibitors are used as a type of hormone therapy for postmenopausal women who have hormone-dependent breast cancer. There are currently three aromatase inhibitors available for clinical use: anastrozole (arimidex); letrozole (femara); exemestane (aromasin).

DCIS (ductal carcinoma in situ):

A noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive. Also called ductal carcinoma in situ and intraductal carcinoma.

Estrogen Receptor (ES-truh-jin reh-SEP-ter) and Tamoxifen:

A protein found inside the cells of the female reproductive tissue, some other types of tissue, and some cancer cells. The hormone estrogen will bind to the receptors inside the cells and may cause the cells to grow. Also called ER.

Learn more about estrogen receptor and tamoxifen at the NCI website.

HER2 and Herceptin:

A specific type of breast cancer called HER2+ (HER2-positive) is caused by an excess of HER2 genes or by over-production of its protein, the HER2 cell surface receptor. HER2 is a member of the epidermal growth factor receptor (ErbB) family of genes which code for protein products known as surface-bound tyrosine kinase proteins. Mutations or over-production of these molecules stimulates cell division and uncontrolled growth. Twenty to 25 percent of breast cancers are HER2+. These tumors tend to grow faster and are generally more likely to recur than tumors that do not overproduce HER2.

Learn more about HER2 at the NCI website.

Invasive Breast Cancer:

Cancer that has spread from where it started in the breast into surrounding, healthy tissue. Most invasive breast cancers start in the ducts (tubes that carry milk from the lobules to the nipple). Invasive breast cancer can spread to other parts of the body through the blood and lymph systems. Also called infiltrating breast cancer.

Sentinel Lymph Node:

The first lymph node to which cancer is likely to spread from the primary tumor. When cancer spreads, the cancer cells may appear first in the sentinel node before spreading to other lymph nodes.

Sentinel Lymph Node Biopsy:

SLN biopsy is a procedure in which the sentinel lymph node is removed and examined under a microscope to determine whether cancer cells are present. SLN biopsy is based on the idea that cancer cells spread (metastasize) in an orderly way from the primary tumor to the sentinel lymph node(s), then to other nearby lymph nodes.

A negative SLN biopsy result suggests that cancer has not spread to the lymph nodes. A positive result indicates that cancer is present in the SLN and may be present in other lymph nodes in the same area (regional lymph nodes). This information may help the doctor determine the stage of cancer (extent of the disease within the body) and develop an appropriate treatment plan.

Learn more about sentinel lymph nodes in breast cancer at the NCI website.