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This glossary forms part of the Progress Educational Trust (PET) project 'Breast Cancer: Chances', supported by the Wellcome Trust.

Autosomal dominant inheritance
The inheritance pattern observed when an alteration (which can be a mutation) in just one copy of a gene on an autosome (a non-sex chromosome) is sufficient to impair cell function, leading to disease.

A test, sold by Myriad Genetics, for mutations in the BRCA1 and BRCA2 genes.

A gene on chromosome 17, which instructs the cell to make a protein that normally helps to repair damaged DNA and suppress cell growth. A person who inherits certain mutations in a BRCA1 gene has a higher risk of getting breast cancer ovarian cancer and certain other types of cancer.

A gene on chromosome 13, which instructs the cell to make a protein that normally helps to repair damaged DNA and suppress cell growth. A person who inherits certain mutations in a BRCA2 gene has a higher risk of getting breast cancer, ovarian cancer and certain other types of cancer.

Breast cancer
Cancer that forms in tissues of the breast. The most common type of breast cancer is ductal carcinoma, which begins in the lining of the milk ducts – thin tubes that carry milk from the lobules (milk glands) of the breast to the nipple. Another type of breast cancer is lobular carcinoma, which begins in the lobules of the breast. If the cancer has spread from where it began to surrounding tissue, it is called invasive breast cancer. Breast cancer occurs in both women and men, although male breast cancer is rare.

A group of diseases that start when the signals that control how much and how often cells divide stop working properly. This causes cells to grow and multiply too much, and eventually to invade other tissues. There are more than 200 known types of cancer, most of which are named after the tissue or organ where they start.
In situ (Latin for 'in position') cancer remains confined to the original tissue where it started.
Invasive cancer spreads to surrounding tissues.
A programme, due to be rolled out from autumn 2014, which will permit the sharing of GP and hospital records from patients cared for by the NHS in England. Researchers from public and private organisations, based anywhere in the world, will be able to apply to use this data.

A structure composed of a very long DNA molecule and associated proteins. Chromosomes carry the majority of the genetic information of an organism, in the form of genes. Humans have 46 chromosomes (23 pairs).

Clinical trial
A research study in which new ways to prevent, detect, diagnose or treat cancer or other diseases are tested on human participants. National and international policies and regulations have been developed to protect the rights, safety and wellbeing of people who participate in clinical trials, and to ensure that trials are conducted according to scientific and ethical principles.

Detecting and describing a disease based on its symptoms (as experienced and reported by the patient) and/or its signs (as observed and understood by a doctor or clinician).
Misdiagnosis is diagnosing a disease inaccurately or incompletely.
Overdiagnosis is diagnosing a disease when symptoms will not appear during a patient's lifetime.

DNA (deoxyribonucleic acid)
A chemical that encodes genetic information. Genes are made of DNA.

The ability of a treatment for a disease to produce the desired or intended beneficial results

Relating to changes in the pattern of gene activity that do not involve any alteration of the DNA sequence.

The basic biological unit of inheritance, made of DNA. Genes are coded instructions for making proteins, or for making other molecules that control the activity of genes.

The extent to which a particular characteristic is inherited. Studies of heritability usually estimate the proportion of observed variation in a particular trait (for example height, or the occurrence of a particular type of cancer) that can be attributed to inherited genetic factors.

HFEA (Human Fertilisation and Embryology Authority)
A UK non-departmental public body which regulates treatment using eggs and sperm, and treatment and research involving human embryos. It sets standards for, and issues licences to, fertility treatment and embryo research centres.

The number of new cases of a disease which are diagnosed in a specific population over a specific time period. Not to be confused with prevalence.

Intellectual property
Creations of the mind to which individuals or organisations are granted exclusive rights, as defined in and protected by law. Those who are granted such rights are said to be the owners of the intellectual property.

An arrangement whereby a public or private organisation undertakes to provide a guarantee of compensation for specified loss, damage, illness, or death, in exchange for payment of a specified premium.

Lead time bias
A statistical distortion that can arise when one test for a disease provides an earlier diagnosis than another test, but there is no effect on eventual disease outcome. For example, lead time bias can make it appear as though people who are diagnosed with cancer as a result of screening programmes survive longer than people who are diagnosed only after symptoms appear.

The surgical removal of one or both breasts.

A temporary agreement to suspend or prohibit an activity.

A change in the DNA sequence of a gene. Some mutations can be inherited, while others cannot – it depends on where and when they occur.

Myriad Genetics
An American molecular diagnostic company, which sells the BRACAnalysis and myRisk Hereditary Cancer tests for gene mutations.

myRisk Hereditary Cancer
A panel of tests sold by Myriad Genetics, for mutations in 25 genes (including BRCA1 and BRCA2) associated with eight types of cancer (including breast cancer).

NICE (National Institute for Health and Care Excellence)
A public body that develops and provides guidance to UK healthcare professionals and others, to ensure that the care they provide is of the best possible quality and offers the best value for money.

The surgical removal of one or both ovaries.

Ovarian cancer
Cancer that forms in tissues of the ovary (one of a pair of female reproductive glands in which the ova, or eggs, are formed). Most ovarian cancers are either ovarian epithelial carcinomas (cancer that begins in the cells on the surface of the ovary) or malignant germ cell tumours (cancer that begins in egg cells).

A form of intellectual property. The owners of a patent are granted a temporary monopoly over an invention (a right to exclude others from making, using or selling it) in exchange for detailed public disclosure of the invention

The probability of a disease or characteristic occurring in a person who inherits a genetic mutation known to cause that same disease or characteristic. A 'highly' penetrant mutation (such as BRCA1 or BRCA2) will result in disease (in this case cancer) occurring in a high proportion of the people who carry that mutation.

Personalised/precision/stratified medicine
An approach to medicine based on taking patients who have or are at risk of a particular disease, and grouping them according to how the disease manifests in them or how they respond to particular treatments (or to prophylaxis). This enables the identification and development of measures that are most effective for particular groups of patients. The ultimate aim is to ensure that all patients get the right treatment at the right time.

PGD (preimplantation genetic diagnosis)
A technique that can enable people to avoid passing gene mutations, and therefore disease predisposition, on to their children. It involves testing the genes of embryos created through IVF.

Increased likelihood of developing a particular disease due to carrying one or more gene mutations and/or having a family history that indicates an increased risk of the disease. Also called genetic susceptibility.

The proportion of people with a disease in a specific population at a specific point in time. Not to be confused with incidence.

Treatment given with the intention of preventing disease, before symptoms of disease appear.

Prostate cancer
Cancer that develops in the prostate (a gland that forms part of the male reproductive system).

An arrangement whereby insurers transfer portions of their risk portfolios to other parties, in order to reduce the likelihood of having to pay a large obligation resulting from an insurance claim.

The possibility or probability of disease, injury or loss.
Absolute risk is the risk that a specific event will occur in a specific group of people, with no further context provided; whereas relative risk is the risk that a specific event will occur in one group of people, considered in comparison with another group of people.
Population risk is the proportion of people in a specific population who will experience a specific event; whereas individual risk is the probability that a specific individual will experience a specific event. Individual risk of a disease may be higher or lower than population risk of a disease, depending on factors such as age, environment, family history and lifestyle.
Lifetime risk is the probability that an individual will experience an event at some point during their entire lifetime. This is not the same as the probability that an individual will experience an event at some point during a specified time period (for example the next year, or the next five years).
The chance component of risk is the objective probability of an event occurring; whereas the burden component of risk is the subjective impact that an event stands to have on an individual, given the individual's specific circumstances and outlook. (The term 'burden' can also have a different meaning – a measure used to assess and compare the impact of different diseases and injuries on populations.)

Risk factor
A variable associated with an increased risk of disease.

A strategy for identifying disease in individuals who have not yet experienced symptoms or received a diagnosis.

The extent to which the side effects of a treatment for a disease, and the impact of the treatment on quality of life, can be tolerated.

A distinct mass of tissue which results from an abnormal growth or abnormal division of cells. Tumours are said to be cancerous if they tend to continue growing uncontrollably, and if they are thought to have the potential to spread to surrounding tissues.

US Supreme Court
The highest federal court in the USA. It consists of a Chief Justice and eight Associate Justices, all of whom are nominated by the US President.