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Page 237 Glossary Absolute risk: a measure of risk over time in a group of individuals; may be used to measure lifetime risk or risk over a narrower time period. Adjuvant therapy: the use of another form of therapy in addition to the primary surgical therapy. It usually refers to hormonal therapy, che motherapy, or radiation. Allele: any one of a series of two or more different genes that occupy the same position (locus) on a chromosome. Amplification: a process by which genetic material is increased. Aneuploidy: a genetically unbalanced condition in which a cell or an organism has a number of chromosomes that is not an exact multiple of the normal chromosome number for that species. Angiogenesis: the formation of new blood vessels. Antigen: a substance that induces the immune system to produce anti bodies that interact specifically with it. Ataxia telangiectasia: an autosomal recessive disorder of the nervous system; affected individuals are sensitive to radiation and have a higher risk of cancer. Atypical hyperplasia: proliferation of cells showing atypical nuclear form, especially as scattered cells. Autosomal: a non-sex-linked form of inheritance (the gene is not found on the X or Y chromosome). Bias: a process at any stage of inference tending to produce results that depart systematically from the true values.
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Page 238 Bioinformatics: use of computers and specialized software to organize and analyze biological information and data. Biomarker: see tumor marker. Biopsy: excision of a small piece of tissue for diagnostic examination; can be done surgically or with needles. Blind study: a study in which the identity and relevant characteristics of the study subjects are concealed from the investigators. BRCA1: a gene located on the short arm of chromosome 17; when this gene is mutated, a woman is at greater risk of developing breast or ovarian cancer, or both, than women who do not have the mutation. BRCA2: a gene located on chromosome 13; a germ-line mutation in this gene is associated with increased risk of breast cancer. Breast lavage: a procedure in which a small catheter is inserted into the nipple and the breast ducts are flushed with fluid to collect breast cells. Breast self-examination: monthly physical examination of the breasts with the intent of finding lumps that could be an early indication of cancer. Carcinogen: any substance or agent that produces or incites cancer. Carcinogenesis: the production or origin of cancer. Carcinoma in situ: a lesion characterized by cytological changes similar to those associated with invasive carcinoma, but with the pathologi cal process limited to the lining epithelium and without visible evi dence of invasion into adjacent structures. Catheter: a tube passed through the body for evacuating or injecting fluids into body cavities. cDNA: complementary DNA synthesized by RNA-directed DNA poly merase using RNA as a template; may be used as a probe for the presence of a gene code. Cell culture: the growth of cells in vitro for experimental purposes. Chromophore: any chemical that when present in a cell displays color. Chromosome: chromosomes carry the genes, the basic units of heredity. Humans have 23 pairs of chromosomes, one member of each pair is from the mother and the other is from the father. Each chromosome can contain hundreds or thousands of individual genes. Clinical breast examination: a physical examination of the breasts, per formed by a doctor or nurse, with the intent of finding lumps that could be an early indication of cancer. Clinical outcome: the end result of a medical intervention, e.g., survival or improved health. Clinical trial: a formal study carried out according to a prospectively defined protocol that is intended to discover or verify the safety and
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Page 239 effectiveness of procedures or interventions in humans. The term may refer to a controlled or uncontrolled trial. Clone: a group of identical DNA molecules derived from one original length of DNA sequence. Comparative genomic hybridization: method used to identify gain or loss of chromosomal material in cells. Computed tomography: an imaging test in which many X-ray images are taken from different angles of a part of the body. These images are combined by a computer to produce cross-sectional pictures of internal organs. Computer-aided detection: use of sophisticated computer programs de signed to recognize patterns in images. Contralateral: originating in or affecting the opposite side of the body. Contrast agent: a substance that enhances the image produced by medical diagnostic equipment such as ultrasound, X ray, magnetic resonance imaging, or nuclear medicine or and imaging-sensitive substance that is ingested or injected intravenously to enhance or increase co Core-needle biopsy: procedure in which a hollow needle is used to remove small cylinders of tissue from a suspected tumor. Cost-effectiveness analysis: methods for comparing the economic efficiencies of different therapies or programs that produce health. Cytogenetics: the study of cytology in relation to genetics. Cytology: the study of formation, structure, and function of cells. Detection: finding disease. Early detection means that the disease is found at an early stage, before it has grown large or spread to other sites. Detection method: the traditional method of measuring the sensitivity of a screening test, in which the sensitivity is calculated as the number of true-positive results divided by the number of true-positive results plus the number of false-negative results. Diagnosis: confirmation of a specific disease usually by imaging procedures and from the use of laboratory findings. Diagnostic mammography: X-ray-based breast imaging undertaken for the purpose of diagnosing an abnormality discovered by physical exam or screening mammography. Digital mammography: see full-field digital mammography. DNA: abbreviation for deoxyribonucleic acid. DNA holds genetic information for cell growth, division, and function. Duct: a hollow passage for gland secretions. In the breast, a passage through which milk passes from the lobule (which makes the milk) to the nipple.
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Page 240 Ductal carcinoma in situ: a lesion in which there is proliferation of abnormal cells within the ducts of the breast, but no visible evidence of invasion into the duct walls or surrounding tissues; sometimes referred to as “precancer” or “preinvasive cancer.” Effectiveness: the extent to which a specific test or intervention, when used under ordinary circumstances, does what it is intended to do. Efficacy: the extent to which a specific test or intervention produces a beneficial result under ideal conditions (e.g., in a clinical trial). Elastography: the measurement of the elastic properties of tissue. Electrical impedance imaging: a procedure by which images are generated by transmitting a low-voltage electrical signal through the tissue. Electrical potential measurements: a method that measures and records altered electrical gradients in tissues. Electronic palpation: use of pressure sensors to quantitatively measure palpable features of the breast such as the hardness and size of lesions. Endoscopy: inspection of body organs or cavities with a flexible lighted tube called an endoscope. Epidemiology: science concerned with defining and explaining the interrelationships of factors that determine disease frequency and distribution. Epigenetics: the study of mechanisms that produce phenotypic effects by altering gene activity without altering the nucletide sequence. Epithelial tissue: those cells that form the outer surface of the body and that line the body cavities and the principal tubes and passageways leading to the exterior. They form the secreting portions of glands and their ducts and important parts of certain sense organs. The cells rest on a basement membrane and lie close to each other, with little intercellular material between them. Etiology: the study of the causes of a disease. Exon: the portions of the DNA sequence in a gene that specify the sequence of amino acids in a polypeptide chain, as well as the beginning and end of the coding sequence. Experimental study: a clinical study in which subjects are randomly assigned to different intervention groups. False-negative result: a test result that indicates that the abnormality or disease being investigated is not present when in fact it is. False-positive result: a test result that indicates that the abnormality or disease being investigated is present when in fact it is not. Familial clusters: a disease occurring in a family more frequently than would be expected by chance.
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Page 241 Fine-needle aspiration: a procedure by which a thin needle is used to draw up (aspirate) samples for examination under a microscope. Flow cytometry: any technique for sorting, selecting, or counting individual cells in a suspension as they pass through a tube; applied especially to techniques involving the detection of a cell-bound fluorescent label and often used in cancer research as well as in screening for chromosomal abnormalities. Fluorescent in situ hybridization: an experimental procedure for localizing a specific gene or DNA sequence within a chromosome based on binding of a complementary, fluorescently labeled segment of RNA or DNA to it. Full-field digital mammography: similar to conventional mammography (film-screen mammography) except that a dedicated electronic detector system is used to computerize and display the X-ray information. Gamma camera: an imaging instrument that records the spatial distribution of radioactive compounds in the human body. Gel electrophoresis: a method for separating proteins or nucleic acid fragments that is carried out in a silica or acrylamide gel under the influence of an electric field. Gene: a functional unit of heredity that occupies a specific place or locus on a chromosome. Genetic marker: a genetic change in cells that is indicative of cancer or malignant potential, or a piece of DNA that lies on a chromosome so close to a gene that the marker and the gene are inherited together. A marker is thus an identifiable heritable spot on a chromosome. A marker can be an expressed region of DNA (a gene) or a segment of DNA with no known coding function. Genome: an organism's entire complement of DNA, which determines its genetic makeup. Germ-line mutation: an inherited mutation found in all cells in the body. Heterogeneous: exhibiting variable characteristics. Heterozygosity: the state of having different alleles at a specific locus in the genome. High-throughput technology: any approach using robotics, automated machines, and computers to process many samples at once. Histology: the study of the microscopic structure of tissue. Hyperplasia: an increase in the number of cells in a tissue or organ, excluding tumor formation. Imaging agents: any substance administered to a patient for the purpose of producing or enhancing an image of the body; includes contrast
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Page 242 agents used with medical imaging techniques such as radiography, computed tomography, ultrasonography, and magnetic resonance imaging, as well as radiopharmaceuticals used with imaging procedures such as single-photon emission computed tomography and positron emission tomography. Immunocytochemistry or immunohistochemistry: a laboratory test that uses antibodies to detect specific biochemical antigens in cells or tissue samples viewed under a microscope; can be used to help classify cancers. Immunology: the study of immunity to diseases. Incidence method: method of measuring the sensitivity of a screening test; calculates the cancer incidence among persons not undergoing screening and the interval cancer rate of persons who are screened. In situ: in position, localized. Intron: an apparently nonfunctional segment of DNA, ranging in size from less than 100 to more than 1,000 nucleotides, which is transcribed into nuclear RNA but which is then removed from the transcript and rapidly degrades. Invasive cancer: cancers capable of growing beyond their site of origin and invading neighboring tissue. Invasive ductal carcinoma: a cancer that starts in the ducts of the breast and then breaks through the duct wall, where it invades the surrounding tissue; it is the most common type of breast cancer and accounts for about 80 percent of breast malignancies. Invasive lobular carcinoma: a cancer that starts in the milk-producing glands (lobules) of the breast and then breaks through the lobule walls to involve the surrounding tissue; accounts for about 15 percent of invasive breast cancers. Lead-time bias: the assumption that identifying and treating tumors at an earlier point in the progression of the disease will necessarily alter the rate of progression and the eventual outcome. Length bias: the assumption that screening tests are more likely to identify slowly growing tumors than those with a fast growth rate. Li-Fraumeni syndrome: a dominant cancer syndrome in which gene carriers have a higher risk of several cancer types, including breast cancer. Linkage analysis: study of the association between distinct genes that occupy closely situated loci on the same chromosome. This results in an association in the inheritance of these genes. Lobular carcinoma in situ: abnormal cells within a breast lobule that have not invaded surrounding tissue; can serve as a marker of future cancer risk.
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Page 243 Localized cancer: a cancer that is confined to the place where it started; that is, it has not spread to distant parts of the body. Loss of heterozygosity: loss of one allele at a specific genetic locus via deletion, usually accompanied by a point mutation in the remaining allele. Magnetic resonance imaging: method by which images are created by recording signals generated from the excitation (the gain and loss of energy) of elements such as the hydrogen of water in tissue in a magnetic field. Magnetic resonance spectroscopy: the study of the alteration and interaction of magnetic sublevels, in which the relevant wavelengths include long microwaves through radio-wave frequencies. Malignant: a tumor that has the potential to become lethal through destructive growth or by having the ability to invade surrounding tissue and metastasize. Malignant transformation: changes that a cell undergoes as it develops the ability to form a malignant tumor. Mammogram: X-ray image of the breast. Mammography: technique for imaging breast tissues with X rays. Mass spectroscopy: a method for separating molecular and atomic particles according to mass by applying a combination of electrical and magnetic fields to deflect ions passing in a beam through the instrument. Medicaid: jointly funded federal-state health insurance program for certain low-income and needy people. It covers approximately 36 million individuals including children; aged, blind, and/or disabled people; and people who are eligible to receive federally assisted income maintenance payments. Medicare: a program that provides health insurance to people age 65 and over, those who have permanent kidney failure, and people with certain disabilities. Menarche: the initial menstrual period. Menopause: permanent cessation of menstrual activity. Messenger RNA: the molecule, also called mRNA, that carries the information from the DNA genetic code to areas in the cytoplasm of the cell that make proteins. Meta-analysis: the use of statistical techniques in a systematic review to integrate the results of the included studies. Metastasis: the ability of cancer cells to move from one part of the body to another, resulting in the growth of a secondary malignancy in a new location. Methylation: the attachment of a methyl group (CH3) to cytosine residues of eukaryotic DNA to form 5-methylcytosine.
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Page 244 Microarray: thousands of different oligonucleotides spotted onto specific locations on glass microscope slides or silicon chips, which are then hybridized with labeled sample DNA or RNA. Microcalcifications: tiny calcium deposits within the breast, singly or in clusters; often found by mammography. They may be a sign of cancer. Modality: a method of application or use of any therapy or medical device. Molecular markers: changes in cells, at the molecular level, that are indicative of cancer or malignant potential. Monoenergetic x-rays: a beam of X rays whose photon energy is found to lie within a very narrow band. Morbidity: injury or illness. Morphology: science of structure and form without regard to function. Mortality: the death rate; ratio of number of deaths to a given population. Mutation: a change either in the base sequence of DNA or in the order, number, or placement of genes on or across chromosomes that may result in a change in the structure or function of a protein. Neoplasm: new growth; a tumor. Nipple aspiration: use of suction to collect breast fluid through the nipple of nonlactating women. Northern analysis: an electroblotting technique for detecting a specific RNA molecule, in which RNA is transferred to a filter and is hybridized to radioactively labeled RNA or DNA. Observational study: a clinical study in which information is collected on groups of individuals who have a specific condition or who have chosen a particular course of medical intervention. Occult tumors: undetected and without symptoms. Oligonucleotide: a small DNA or RNA molecule composed of a few nucleotide bases. Oncology: the branch of medicine dealing with tumors. Optical imaging: use of light, usually in the near-infrared range, to produce an image of tissue. Overdiagnosis: labeling an abnormality as cancer when it in fact is not likely to become a lethal cancer. p53: a tumor suppressor gene commonly mutated in cancer. Palpable tumor: a tumor that can be felt during a physical examination. Phenotype: the physical characteristics or makeup of an individual. Photonics: the technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The
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Page 245 science includes light emission, transmission, deflection, amplification, and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. Polymerase chain reaction: a process for amplifying a DNA molecule up to 106- to 109-fold. Polymorphism: the regular and simultaneous occurrence in a population of two or more alleles of a gene in which the frequency of the rarer of the alleles is greater than can be explained by recurrent mutation alone. Positional cloning: cloning a gene simply on the basis of knowing its position in the genome without any idea of the function of that gene. Positive predictive value: a measure of accuracy for a screening or diagnostic test; indicates what portion of those with an abnormal test result actually have the disease. Positron emission tomography: use of radioactive tracers such as labeled glucose to identify regions in the body with altered metabolic activity. Premalignant: changes in cells that may, but that do not always, become cancer. Also called “precancer.” Prevalence: a measure of the proportion of persons in the population with a particular disease at a given time. Prognosis: prediction of the course and end of disease and the estimate of chance for recovery. Progression: the growth or advancement of cancer, indicating a worsening of the disease. Prophylactic bilateral mastectomy: surgical removal of both breasts with the intent of reducing the risk of developing breast cancer later in life. Proprietary rights: exclusive rights held by a private individual or corporation under a trademark or patent. Proteome: all of the proteins produced by a given species, just as the genome is the totality of the DNA possessed by that species. Protooncogene: genes that promote cell growth and multiplication; normally found in all cells, but may undergo mutations that activate them, causing uncontrolled growth. Randomization: a method that uses chance to assign participants to comparison groups in a trial by using a random-numbers table or a computer-generated random sequence. Random allocation implies that each individual being entered into a trial has the same chance of receiving each of the possible interventions. Relative risk: a comparative measure of risk based on a comparison of disease incidence in two populations.
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Page 246 Reverse transcriptase: an RNA-dependent DNA polymerase, found in viruses, that catalyzes the synthesis of DNA from deoxyribonucleoside 5'-triphosphates, using RNA as a template. Risk: a quantitative measure of the probability of developing or dying from a particular disease such as cancer. Scintimammography: use of radioactive tracers to produce an image of the breast. Screen-film mammography: conventional mammography in which the X rays are recorded on film. Screening: systematic testing of an asymptomatic population to determine the presence of a particular disease or certain risk factors known to be associated with the disease. Screening mammography: X-ray-based breast imaging in an asymptomatic population with the goal of detecting breast tumors at an early stage. Sensitivity: a measure of how often a test correctly identifies women with breast cancer. Signal transduction: the biochemical events that conduct the signal of a hormone growth factor from the cell exterior, through the cell membrane, and into the cytoplasm. This involves a number of molecules, including receptors, proteins, and messengers. Soft copy: image display on a computer screen rather than on film. Somatic mutation: uninherited mutation, acquired in cells during a person's lifetime. Specificity: a measure of how often a test correctly identifies a woman as not having breast cancer. Specimen bank: stored patient tissue samples that are used for biomedical research (also tumor or tissue banks). Spectroscopy: analytical use of an instrument that separates radiant energy into its component frequencies or wavelengths by means of a prism or grating to form a spectrum for inspection. Stereotactic breast biopsy: use of breast images (X ray or ultrasound) taken at various angles to generate a three-dimensional image for plotting the exact position of the suspicious lesion and for guiding the placement of a biopsy needle. Surrogate end points: short-term, intermediate end points in a clinical study that are thought to be representative or predictive of longer-term outcomes. Systemic therapy: treatment involving the whole body, usually using drugs. Telemammography: the process of satellite or long-distance transmission of digital mammography for consultation.
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Page 247 Thermography: use of a device that detects and records the heat produced by tissues to generate an image. Thermotherapy: use of lasers or high-intensity ultrasound to heat and destroy tumor cells. Tissue array: small cylinders of tissue punched from 1,000 individual tumor biopsy specimens embedded in paraffin. These cylinders are then arrayed in a large paraffin block, from which 200 consecutive tissue sections can be cut, allowing rapid analysis of multiple arrayed samples by immunohistochemistry or in situ hybridization. Tomography: any of several techniques for making X-ray pictures of a predetermined plane section of a solid object by blurring out the images of other planes. Tomosynthesis: a variation of tomography in which several photographs of a patient are taken at different angles, and back-projection of the resulting radiographs produces a light distribution in a chosen three-dimensional volume of space that replicates the same volume in the patient. Transcription: the first step of protein biosynthesis, in which DNA directs the production of RNA. Tumorigenesis: the induction of the malignant growth of abnormal cells. Tumor marker: any substance or characteristic that indicates the presence of a malignancy. Tumor suppressor genes: genes that slow cell division or that cause cells to die at the appropriate time. Mutations in these genes can lead to uncontrolled cell growth and the development of cancer. Ultrasound: use of inaudible, high-frequency sound waves to create an image of the body. Virtual reality imaging: interactive computer graphic simulations that can be used to produce a three-dimensional visualization of an organ or tissue.
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Representative terms from entire chapter: