hormone receptor test: A test to measure the amount of certain proteins, called hormone receptors, in breast cancer tissue. Hormones can attach to these proteins. A high level of hormone receptors means hormones probably help the cancer grow.

hormones: Chemicals produced by glands in the body and circulated in the bloodstream. Hormones control the actions of certain cells or organs.

infertility: The inability to produce children.

inflammatory breast cancer: A type of breast cancer in which the breast looks red and swollen, and feels warm. The skin of the breast may also show the pitted appearance called peau d'orange (like the skin of an orange). The redness and warmth occur because the cancer cells block the lymph vessels in the skin.

invasive cancer: Cancer that has spread beyond the layer of tissue in which it developed and is growing into surrounding, healthy tissues. Also called infiltrating cancer.

lobe: A portion of an organ such as the liver, lung, breast or brain.

lobular carcinoma in situ (LOB-yoo-lar kar-sin-O-ma in SYE-too): LCIS. Abnormal cells found in the lobules of the breast. This condition seldom becomes invasive cancer. However, having lobular carcinoma in situ increases one's risk of developing breast cancer in either breast.

lobule (LOB-yule): A small lobe or subdivision of a lobe.

local therapy: Treatment that affects cells in the tumor and the area close to it.

lumpectomy (lump-EK-toe-mee): Surgery to remove the tumor and a small amount of normal tissue around it.

lymph (limf): The almost colorless fluid that travels through the lymphatic system and carries cells that help fight infection and disease.

lymph nodes: Small organs located throughout the body along the channels of the lymphatic system. The lymph nodes store special cells that fight infection and other diseases. Clusters of lymph nodes are found in the underarms, groin, neck, chest and abdomen. Also called lymph glands.

lymphatic system (lim-FAT-ik): The tissues and organs that produce, store and carry white blood cells that fight infection and other diseases. This system includes the bone marrow, spleen, thymus and lymph nodes, and a network of thin tubes that carry lymph and white blood cells. These tubes branch, like blood vessels, into all the tissues of the body.

lymphedema (LIMF-eh-DEE-ma): A condition in which excess lymph collects in tissue and causes swelling. It may occur in the arm or leg after lymph vessels or lymph nodes in the underarm or groin are removed.