Glossary

Absolute risk: The chance of developing a specific disease over a specified time period.

Allele: An allele is one of two or more forms of a gene that may occupy a given locus on the chromosome. Sometimes, different alleles can result in different traits, such as color. At other times, different alleles will have the same result in the expression of a gene.

Atypical hyperplasia: A benign (non-cancerous) condition in which breast tissue has certain abnormal features. This condition increases the risk of breast cancer.

Benign: A non-cancerous growth that does not spread to nearby tissues or spread to other parts of the body. A benign tumor may grow but is localised.

Biopsy: The removal of a sample of tissue for purposes of diagnosis. The sample of tissue may be examined under a microscope or the diagnosis may be achieved by other means such as by analysis of chromosomes or genes.

BRCA1 and BRCA2 genes: BRCA1 and BRCA2 are human genes that belong to a class of genes known as tumor suppressors. Mutation of these genes has been linked to hereditary breast and ovarian cancer. A woman's risk of developing breast and/or ovarian cancer is greatly increased if she inherits a deleterious (harmful) BRCA1 or BRCA2 mutation. Men with these mutations also have an increased risk of breast cancer. The names BRCA1 and BRCA2  stand for breast cancer susceptibility gene 1 and breast cancer susceptibility gene 2, respectively.

Breast cancer: Breast cancer is a malignant (cancerous) growth that begins in the tissues of the breast.

Breast density: Describes the relative amount of different tissues present in the breast. A dense breast has less fat than glandular and connective tissue. Mammogram films of breasts with higher density are harder to read and interpret than those of less dense breasts.

Cancer: A general term for more than 100 diseases in which there is an uncontrolled, abnormal growth of cells.  In some cases, cancer cells can spread through the bloodstream and lymphatic system to other parts of the body.


Chemoprevention/chemoprophylaxis: Refers to the administration of a medication for the purpose of preventing disease or infection.

CT scan: A special type of X-ray that provides a three-dimensional picture of the inside of the body. The initials stand for "computerized tomography."

DNA: Deoxyribonucleic acid. The molecule that encodes our genetic information.

Duct: A tube in the breast through which milk passes from the lobules to the nipple.


Ductal carcinoma in situ (DCIS): Ductal carcinoma in situ (DCIS) is the presence of abnormal cells inside a milk duct in the breast. DCIS is considered the earliest form of breast cancer. DCIS is non-invasive, meaning it hasn't spread out of the milk duct to invade other parts of the breast.

Estrogen: Estrogen is a female hormone produced by the ovaries which stimulates and maintains female sex characteristics. They are either natural or synthetic. Estrogens are used to treat menstrual and menopausal disorders and are also used as oral contraceptives.


Estrogen receptor: A hormone receptor present in some cell types which binds to the hormone 17β-estradiol (estrogen). Binding of estrogen to this receptor can have several effects, including stimulating cell growth.

Family history: The family structure and relationships within the family, including information about diseases in family members.

Gail test: A computer program that uses personal and family history to estimate a woman’s chance of developing breast cancer.

Gene: The basic unit of heredity found in all cells.

Genetic: Having to do with genes and genetic information.

Genetic predisposition: An inherited genetic pattern that makes one susceptible to a certain disease. Having a genetic predisposition for a disease does not mean that you will get that disease, but your risk may be higher than that of the general population.

Genome: All of the genetic information contained within a cell.

Genotype: The genetic constitution of an organism, as distinguished from its appearance or phenotype; often used to refer to the composition of one or a few genes of interest.

Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.


Hyperplasia: The enlargement of an organ or tissue caused by an increase in the reproduction rate of its cells, often as an initial stage in the development of cancer.

Invasive: Referring to cancer cells that have spread beyond normal boundaries.

Lifetime risk: This is the probability at the day of birth, that an individual will get a given disease sometime during their lifetime. 

Lobe: A part of the breast, each breast contains 15 to 20 lobes.

Lobule: Smaller lobes located inside the main lobes. At the end of each lobule are tiny “bulbs” that produce milk.

Lobular Carcinoma in-situ (LCIS): Lobular carcinoma in situ (LCIS) is an uncommon condition in which abnormal cells form in the lobules or milk glands in the breast. LCIS isn't cancer. But being diagnosed with LCIS indicates that you have an increased risk of developing breast cancer.


Loci: In the field of genetics a locus (plural loci) is the specific location of a gene or DNA sequence on a chromosome. A variant of the DNA sequence at a given locus is called an allele.

Lymph: An almost colorless fluid that travels through the lymphatic system and carries cells that help fight infection and disease.

Lymph node: Also sometimes referred to as lymph glands, lymph nodes are small rounded or bean-shaped masses of lymphatic tissue. Lymph nodes are located in many places throughout the body. The lymph nodes are critical for the body's immune response and are principal sites where many immune reactions are initiated.

Lymphatic system: A circulatory system that includes an extensive network of lymph vessels and lymph nodes. The lymphatic system helps coordinate the immune system’s function to protect the body from infections and foreign substances.

Malignant: Cancerous, can spread to other parts of the body.

Magnetic Resonance Imaging (MRI): A 3-dimensional view of the breasts that uses a magnet and radio waves to detect breast abnormalities. It is a highly sensitive tool for detecting breast cancer.

Mammogram: An X-ray of the breast used to detect abnormal growths or changes in the breast tissue.


Mastectomy: Removal of the whole breast.

Menarche: The first menstrual cycle.

Menopause: The time in a woman's life when menstrual periods permanently stop; it is also called the "change of life." Menopause is the opposite of the menarche.


Menstrual: Pertaining to menstruation, as in last menstrual period, menstrual cramps, menstrual cycle, and premenstrual syndrome.

Metastasis: The name for a cancer that spreads to another part of the body. When cancer cells metastasize and cause secondary tumors, the cells in the secondary tumor are like those in the original cancer.

Metastatic breast cancer: The name for breast cancer that has spread to another part of the body.

Mutation: A permanent change, a structural alteration, in the DNA.

Oncology: The field of medicine devoted to cancer.

Post-menopause: The time after the cessation of menstrual periods.

Pre-menopause: The time when ovaries are functioning normally with regular periods and no menopausal symptoms.

Progesterone: A female hormone and the principal progestational hormone that is made mainly by the corpus luteum in the ovary and by the placenta. Progesterone prepares the lining (endometrium) of the uterus (the womb) to receive and sustain the fertilized egg and so permits pregnancy. Similarly refers to synthetic versions of the hormone.

Prognosis: The probable outcome or course of a disease, the chance of recovery.


Prophylactic treatment: Treatment used to prevent a disease from developing.

Relative Risk: Relative risk is the risk of an event (or of developing a disease) relative to exposure to a particular risk factor. Relative risk is calculated by dividing the frequency of the disease in a group exposed to a risk factor by the frequency of disease in an unexposed group.

Risk factor: Something that increases a person’s chance of developing a disease.

Single nucleotide polymorphisms: A single-nucleotide polymorphism (SNP, pronounced snip) is a DNA sequence variation occurring when a single nucleotide -- A, T, C, or G -- in the genome (or other shared sequence) differs between members of a species or paired chromosomes in an individual.

Sporadic: Occurring upon occasion or in a seemingly random way. In the case of breast cancer, without any obvious link to family history.

Tumor: An abnormal mass of tissue. Tumors can be benign or malignant (cancerous).

X-ray: High-energy electromagnetic radiation used in low doses to diagnose diseases, and used in high doses to treat cancer.