Plain-language definitions of 112 common cancer, oncology, and regenerative medicine terms. Last updated June 2026.
Educational information, not medical advice. This glossary is provided for general education only. It does not diagnose, treat, or prescribe, and it does not create a doctor and patient relationship. Definitions are written in plain language and are grounded in public references from the National Cancer Institute and other public sources, cited per term. Always consult a licensed physician about your own health. Do not delay or disregard professional medical care based on anything you read here.
A cancer that begins in the gland-like cells of epithelial tissue, the lining that covers organs and produces fluids such as mucus. Many common cancers, including most cancers of the colon, breast, prostate, lung, and pancreas, are adenocarcinomas. Source: NCI Dictionary of Cancer Terms
Additional treatment given after the main treatment to lower the chance that a cancer will come back. It may include drugs, radiation, or other approaches. Source: NCI Dictionary of Cancer Terms
Any substance that causes the immune system to respond. Certain antigens are found on cancer cells and can help the immune system or tests recognize them. Source: NCI Dictionary of Cancer Terms
A normal, programmed process by which cells die in an organized way. Cancer cells often avoid apoptosis, which lets them keep growing. Source: NCI Dictionary of Cancer Terms
Describes a growth or tumor that is not cancer. A benign tumor does not spread to other parts of the body, though it may still grow. Source: NCI Dictionary of Cancer Terms
A biological molecule found in blood, other body fluids, or tissue that signals a normal or abnormal process, or a condition such as cancer. Biomarkers are used to help find disease and learn how a tumor behaves. Source: NCI Dictionary of Cancer Terms
The removal of a small sample of cells or tissue so it can be examined under a microscope. A biopsy is one of the main ways doctors check whether an abnormal area is cancer. Source: NCI Dictionary of Cancer Terms
A procedure in which only part of a lump or suspicious area is removed so it can be examined under a microscope. Source: NCI Dictionary of Cancer Terms
The removal of tissue or fluid with a needle for examination under a microscope. It is also called a needle biopsy and is a less invasive way to sample a suspicious area. Source: NCI Dictionary of Cancer Terms
The soft, spongy tissue in the center of most bones where blood cells are made. Some cancers start in the bone marrow, and it can be affected by cancer treatment. Source: NCI Dictionary of Cancer Terms
A type of radiation treatment in which a sealed radioactive source is placed inside or close to the area being treated. It is also called internal radiation therapy. Source: NCI Dictionary of Cancer Terms
A gene that normally helps repair damaged DNA and control cell growth. Certain inherited changes in BRCA1 are linked to a higher risk of breast, ovarian, and some other cancers. Source: NCI Dictionary of Cancer Terms
A gene that helps repair damaged DNA. Inherited changes in BRCA2 raise the risk of breast, ovarian, prostate, and some other cancers. Source: NCI Dictionary of Cancer Terms
A group of diseases in which abnormal cells divide without normal control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. Source: NCI Dictionary of Cancer Terms
Cancer found in one or more parts of the body for which the original starting site cannot be identified. It is also called occult primary cancer. Source: NCI Dictionary of Cancer Terms
Any substance or exposure that can lead to the development of cancer. Examples studied by scientists include tobacco smoke, certain chemicals, and some forms of radiation. Source: NCI Dictionary of Cancer Terms
A cancer that starts in epithelial cells, the cells that line the skin and the inside surfaces of organs. Carcinomas are the most common type of cancer. Source: NCI Dictionary of Cancer Terms
Abnormal cells that look like cancer under a microscope but are still confined to the place where they first formed and have not spread into nearby tissue. It is sometimes called stage 0. Source: NCI Dictionary of Cancer Terms
The use of drugs to stop the growth of cancer cells, usually by killing them or slowing their ability to divide. Chemotherapy may be given by mouth, by injection, or into a vein. Source: NCI Dictionary of Cancer Terms
A research study that tests how well a medical approach works in people. Clinical trials are carried out in carefully designed phases and follow strict scientific and ethical rules. Source: NCI Dictionary of Cancer Terms
An imaging test that uses a computer linked to an x-ray machine to make detailed, cross-sectional pictures of areas inside the body. It is also called computed tomography. Source: NCI Dictionary of Cancer Terms
The study of individual cells under a microscope. Cytology is used to look for changes in cells that may signal disease, such as in a Pap test. Source: NCI Dictionary of Cancer Terms
Describes something that is toxic to cells, meaning it can damage or kill them. Many chemotherapy drugs are cytotoxic to dividing cells. Source: NCI Dictionary of Cancer Terms
The process of identifying a disease by its signs, symptoms, and the results of tests. A cancer diagnosis is usually confirmed by examining tissue under a microscope. Source: NCI Dictionary of Cancer Terms
In cancer, a description of how much tumor cells look and act like the normal cells they came from. Well-differentiated cells resemble normal cells, while poorly differentiated cells look more abnormal. Source: NCI Dictionary of Cancer Terms
The molecule inside cells that carries genetic information and passes it from one generation of cells to the next. Damage to DNA can play a role in the development of cancer. Source: NCI Dictionary of Cancer Terms
Cells that look abnormal under a microscope but are not cancer. Dysplasia may go away on its own, or in some cases it can be an early warning change that needs monitoring. Source: NCI Dictionary of Cancer Terms
A procedure that uses a thin, lighted tube to look inside the body. Endoscopy can let a doctor examine internal organs and take tissue samples. Source: NCI Dictionary of Cancer Terms
The basic unit of heredity, made of DNA, that carries instructions for making proteins and controlling how cells work. Changes in genes can contribute to cancer. Source: NCI Dictionary of Cancer Terms
Laboratory tests that look for changes in genes or chromosomes. In cancer care, genetic testing can identify inherited changes that affect a person's risk. Source: NCI Dictionary of Cancer Terms
The complete set of DNA in a cell or organism. Studying a tumor's genome can reveal changes that drive a cancer. Source: NCI Dictionary of Cancer Terms
A description of how abnormal cancer cells and tissue look under a microscope. Grade gives a sense of how quickly a tumor is likely to grow and is different from stage. Source: NCI Dictionary of Cancer Terms
The study of tissues and cells under a microscope. Histology is used to identify the type of cancer and describe its features. Source: NCI Dictionary of Cancer Terms
Treatment that adds, blocks, or removes hormones to affect cancers that use hormones to grow, such as some breast and prostate cancers. It is also called endocrine therapy. Source: NCI Dictionary of Cancer Terms
A type of care that focuses on comfort and quality of life for people in the final phase of a serious illness, along with support for their families. It does not aim to cure the illness. Source: NCI Dictionary of Cancer Terms
A type of treatment that uses or supports the body's own immune system to fight disease, including some cancers. It is also called biological therapy. Source: NCI Dictionary of Cancer Terms
The number of new cases of a disease, such as a specific cancer, that occur in a defined group of people over a set period of time. Source: NCI Dictionary of Cancer Terms
A Latin term meaning "in place." In cancer, it describes abnormal cells that remain where they first formed and have not spread to nearby tissue. Source: NCI Dictionary of Cancer Terms
Cancer that has spread beyond the layer of tissue where it started and grown into nearby healthy tissue. It is also called infiltrating cancer. Source: NCI Dictionary of Cancer Terms
A cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood. Source: NCI Dictionary of Cancer Terms
Surgery to remove a tumor from the breast along with a small amount of normal tissue around it, rather than removing the whole breast. Source: NCI Dictionary of Cancer Terms
A small, bean-shaped structure that is part of the body's immune system. Lymph nodes filter lymph fluid and are often checked to see whether cancer has spread. Source: NCI Dictionary of Cancer Terms
A cancer that begins in cells of the lymph system, part of the body's immune defenses. The two main groups are Hodgkin lymphoma and non-Hodgkin lymphoma. Source: NCI Dictionary of Cancer Terms
Describes cells or tumors that are cancer. Malignant tumors can invade nearby tissue and spread to other parts of the body. Source: NCI Dictionary of Cancer Terms
An x-ray picture of the breast used to look for early signs of breast cancer in people who may not have symptoms. Source: NCI Dictionary of Cancer Terms
The edge of tissue removed during surgery. A clear, or negative, margin means no cancer cells were seen at the outer edge, suggesting the visible tumor was removed. Source: NCI Dictionary of Cancer Terms
A lump in the body. A mass may be caused by many conditions, and tests are needed to learn whether it is benign or cancer. Source: NCI Dictionary of Cancer Terms
Surgery to remove all or part of the breast. It is sometimes done to treat or to reduce the risk of breast cancer. Source: NCI Dictionary of Cancer Terms
The spread of cancer cells from the place where they first formed to another part of the body. The new tumors are the same type of cancer as the original one. Source: NCI Dictionary of Cancer Terms
Cancer that has spread from the part of the body where it started to other parts of the body. It is sometimes called stage IV or advanced cancer. Source: NCI Dictionary of Cancer Terms
An imaging test that uses a magnet, radio waves, and a computer to make detailed pictures of areas inside the body. It is also called magnetic resonance imaging. Source: NCI Dictionary of Cancer Terms
A change in the sequence of DNA in a cell. Some mutations are inherited, while others happen over a person's lifetime and can contribute to cancer. Source: NCI Dictionary of Cancer Terms
A changed form of a gene that can help turn a normal cell into a cancer cell when it is altered or present in too many copies. Source: NCI Dictionary of Cancer Terms
A doctor who specializes in diagnosing and treating cancer. Types include medical, surgical, and radiation oncologists. Source: NCI Dictionary of Cancer Terms
Care that aims to improve quality of life by preventing or relieving symptoms and side effects of a disease and its treatment. It can be given along with treatment meant to address the disease itself. Source: NCI Dictionary of Cancer Terms
A doctor who identifies diseases by studying cells and tissues under a microscope. Pathologists play a central role in confirming a cancer diagnosis. Source: NCI Dictionary of Cancer Terms
A document that describes what a pathologist found when examining tissue or cells removed from the body. It often includes the cancer type, grade, and other features. Source: NCI Dictionary of Cancer Terms
A measure of how well a person can carry out ordinary daily activities. It helps care teams understand overall condition and plan care. Source: NCI Dictionary of Cancer Terms
An imaging test that uses a small amount of radioactive sugar to create pictures showing how tissues and organs are working. It can help locate areas of unusual activity in the body. Source: NCI Dictionary of Cancer Terms
The first step in testing a new approach in people. A Phase I trial focuses mainly on safety, including how a treatment should be given and the dose that can be tolerated, in a small number of participants. Source: NCI Dictionary of Cancer Terms
A study that tests whether a new approach has an effect on a certain condition or disease and continues to look at its safety, usually in a larger group than a Phase I trial. Source: NCI Dictionary of Cancer Terms
A study that compares a new approach with the current standard approach in a large group of people, while continuing to monitor safety. Results help show which works better. Source: NCI Dictionary of Cancer Terms
A study done after a treatment has been approved for use, to gather more information about its long-term safety and how it works in larger and more varied groups of people. Source: NCI Dictionary of Cancer Terms
Describes cells or tissue that are not yet cancer but that have a higher than normal chance of becoming cancer. It is also called premalignant. Source: NCI Dictionary of Cancer Terms
The likely course and outcome of a disease, and the chance of recovery, based on patterns seen in many people. A prognosis is an estimate, not a certainty for any one person. Source: NCI Dictionary of Cancer Terms
The use of high-energy radiation to damage cancer cells and keep them from growing. It can be delivered from a machine outside the body or from a source placed inside the body. Source: NCI Dictionary of Cancer Terms
Cancer that has come back after a period when it could not be detected. It may return in the same place, nearby, or in another part of the body. Source: NCI Dictionary of Cancer Terms
A decrease in or disappearance of the signs and symptoms of cancer. In complete remission, signs and symptoms cannot be detected, though cancer may still be present in the body. Source: NCI Dictionary of Cancer Terms
Anything that increases the chance of developing a disease such as cancer. Having a risk factor does not mean a person will get cancer, and many people with risk factors never do. Source: NCI Dictionary of Cancer Terms
A cancer that begins in bone or in the soft, connective, and supporting tissues of the body, such as muscle, fat, blood vessels, or cartilage. Source: NCI Dictionary of Cancer Terms
Checking for a disease such as cancer in people who do not have symptoms. The goal of screening is to find disease at an early stage. Source: NCI Dictionary of Cancer Terms
The first lymph node to which cancer is likely to spread from a primary tumor. Examining it can help show whether cancer has begun to travel through the lymph system. Source: NCI Dictionary of Cancer Terms
An unwanted effect of a treatment, drug, or other approach. Side effects can be mild or serious and vary from person to person. Source: NCI Dictionary of Cancer Terms
A description of the extent of a cancer in the body, including the size of the tumor and whether it has spread. Stage helps guide care and is usually written as a number from 0 to IV. Source: NCI Dictionary of Cancer Terms
The process of finding out how much cancer is in the body and where it is located. Staging often uses imaging tests, lab tests, and tissue samples. Source: NCI Dictionary of Cancer Terms
Treatment that experts widely accept and that is in common use for a given condition, based on available evidence. Source: NCI Dictionary of Cancer Terms
The percentage of people in a study or group who are alive for a certain period of time after a diagnosis. It is a statistic about a group, not a prediction for one person. Source: NCI Dictionary of Cancer Terms
In cancer, the experience of living with, through, and beyond a cancer diagnosis. Survivorship includes physical, emotional, and practical concerns from diagnosis onward. Source: NCI Dictionary of Cancer Terms
A type of treatment that uses drugs or other substances to act on specific molecules involved in the growth and spread of cancer cells. Source: NCI Dictionary of Cancer Terms
A common system for describing the extent of many cancers. T describes the size of the main tumor, N whether nearby lymph nodes contain cancer, and M whether the cancer has spread to distant parts of the body. Source: NCI Dictionary of Cancer Terms
An abnormal mass of tissue that forms when cells grow and divide more than they should or do not die when they should. A tumor may be benign or malignant. Source: NCI Dictionary of Cancer Terms
The total amount of cancer in the body, including the number, size, or volume of tumors. It is also called tumor load. Source: NCI Dictionary of Cancer Terms
A substance found in the body that may be present in higher amounts when cancer is present. Tumor markers can help with diagnosis and with following how a cancer changes over time. Source: NCI Dictionary of Cancer Terms
A type of gene that helps control cell growth. When a tumor suppressor gene is changed so it no longer works, cells may grow out of control and form cancer. Source: NCI Dictionary of Cancer Terms
An imaging method that uses high-energy sound waves to create pictures of areas inside the body. It is also called ultrasonography. Source: NCI Dictionary of Cancer Terms
A type of blood cell that helps the body fight infection and other disease. White blood cell levels are often watched during cancer treatment. Source: NCI Dictionary of Cancer Terms
Regenerative Medicine Terms
General scientific concepts only. The terms below are defined as general educational and scientific concepts. Their presence here does not mean this site offers, provides, recommends, or endorses any of them as a treatment, and no claim of safety, effectiveness, or outcome is made or implied. These definitions are grounded in the UPMC Regenerative Medicine glossary and the NCI Dictionary of Cancer Terms.
A type of stem cell found among specialized cells in tissues such as bone marrow. It can usually develop into the cell types of the tissue where it is found. Source: NCI Dictionary of Cancer Terms
A scientific term describing cells or tissue taken from a donor and used in a different person of the same species. It is used here only as a general educational concept. Source: UPMC Regenerative Medicine Glossary
A scientific term describing cells or tissue that come from a person's own body. It is presented here only as a general educational concept. Source: NCI Dictionary of Cancer Terms
A general term in science and medicine for a product made from living organisms or their cells. The word is defined here only to explain the concept, not any specific product. Source: NCI Dictionary of Cancer Terms
A broad scientific field that studies the use of living cells as a way to research repair of tissue. It is described here as a general concept in regenerative medicine, not as a service or treatment. Source: UPMC Regenerative Medicine Glossary
A type of protein made by cells that helps control the activity of other cells, including cells of the immune system. Cytokines are studied across many areas of biology. Source: NCI Dictionary of Cancer Terms
The biological process by which an unspecialized cell, such as a stem cell, develops into a more specialized cell type with a particular function. Source: UPMC Regenerative Medicine Glossary
A very small membrane-bound particle released by many types of cells. Exosomes are a kind of extracellular vesicle that can carry proteins and genetic material and are studied by scientists for their role in communication between cells. Source: UPMC Regenerative Medicine Glossary
A general term for tiny packets enclosed by a membrane that cells release into their surroundings. Exosomes are one type. Researchers study them to understand how cells signal to one another. Source: UPMC Regenerative Medicine Glossary
A naturally occurring substance, usually a protein, that can signal cells to grow, divide, or mature. Growth factors are studied across many areas of biology. Source: NCI Dictionary of Cancer Terms
A type of adult stem cell, studied by scientists, that can give rise to several connective tissue cell types such as bone, cartilage, and fat cells. The term is presented here only as a general scientific concept. Source: UPMC Regenerative Medicine Glossary
An early descendant of a stem cell that can develop into one or more kinds of specialized cells but has a more limited ability to renew itself than a stem cell. Source: UPMC Regenerative Medicine Glossary
A scientific field that studies ways the body might repair, replace, or restore damaged cells, tissues, or organs. It is described here only to explain the field, not to describe any service offered. Source: UPMC Regenerative Medicine Glossary
In tissue engineering, a supporting structure, often a specially made material, that researchers use to help cells organize and grow into tissue-like forms. Source: UPMC Regenerative Medicine Glossary
An unspecialized cell that can renew itself and can develop into more specialized cell types. Stem cells are studied widely in biology and medicine. Source: UPMC Regenerative Medicine Glossary
A scientific field that combines cells, engineering, and materials science to study how functional tissue might be built or supported in the laboratory. Source: UPMC Regenerative Medicine Glossary