Glossary

Cancer terms explained in plain language. Definitions are based on National Cancer Institute resources, including the NCI Dictionary of Cancer Terms.

Acupressure: Applying pressure to specific points on the body, such as a point on the wrist, which may help relieve nausea when used together with medication.
Acute leukemia: A type of leukemia that grows quickly.
Acute pain: Pain that may feel sharp, come on quickly, and often lasts only a short time.
Addiction: Compulsive drug-seeking behavior and the inability to stop taking a drug despite harmful consequences.
Adjuvant chemotherapy: Chemotherapy given to destroy cancer cells that may remain after surgery or radiation therapy.
Adjuvant therapy: Treatment given to lower the risk that cancer will come back after the main treatment.
Allogeneic transplant: A transplant in which the stem cells come from someone else, such as a relative or matched donor.
Alopecia: The medical word for hair loss, including hair loss caused by some cancer treatments.
Anemia: Having too few red blood cells to carry enough oxygen to the body's tissues, which can lower your energy level.
Anesthesia: Drugs or other substances that cause loss of feeling or awareness. Anesthesia can be local, regional, or general, and may be used during some biopsies.
Angiogenesis inhibitors: Targeted therapies that interfere with the signals a tumor uses to form new blood vessels, keeping tumors from getting the blood supply they need to grow.
Anticipatory nausea and vomiting: Nausea and vomiting that happen before treatment begins, often triggered by the smells, sights, and sounds of the treatment room after an earlier bad experience.
Antiemetics: Medicines (also called antinausea drugs) that work to prevent and relieve nausea and vomiting.
Anxiety: Extra worry, trouble relaxing, and feeling tense; it can cause physical symptoms like a rapid heartbeat, headaches, and trouble concentrating.
Apoptosis: Programmed cell death, the normal process by which cells are told to stop dividing or to die. Cancer cells ignore these signals.
Appetite loss: A decrease in the desire to eat, which is common in people with cancer and often leads to eating less than the body needs.
Appetite stimulant: A medicine that increases appetite and can cause weight gain.
Autologous transplant: A transplant in which the stem cells come from you, the person with cancer.
Benign: Not cancer. Benign tumors do not spread into or invade nearby tissues, and when removed they usually do not grow back.
Benign tumor: A tumor whose cells do not invade nearby tissues or spread to other parts of the body.
Bias: When a trial's results are affected by human choices or other factors not related to the treatment being tested.
Biological therapy: A type of treatment that uses substances made from living organisms to treat cancer.
Biomarker test: A molecular test done on a tumor or body fluid that can help identify the best treatments for an individual patient.
Biomarker testing: Testing that looks for information about a cancer, including targets that could help choose a treatment.
Biopsy: A procedure in which a doctor removes a sample of abnormal tissue so a pathologist can examine it under a microscope. It is often the only way to tell for sure if you have cancer.
Bone marrow transplant: A stem cell transplant in which the blood-forming stem cells come from the bone marrow.
Brachytherapy: Internal radiation therapy that uses a solid source, such as seeds, ribbons, or capsules, placed in or near the tumor.
Breakthrough pain: Pain that comes on suddenly while you are taking medicine to manage chronic pain; it usually lasts a short time and may be intense.
Cachexia: A wasting syndrome that causes weakness, muscle loss, and weight loss in some people with cancer; it is different from ordinary weight loss and treated differently.
Cancer: A disease in which some of the body's cells grow uncontrollably and spread to other parts of the body.
Cancer fatigue: A condition caused by cancer or its treatment in which you feel exhausted or extremely tired, and which is not fully relieved by rest or sleep. Also called cancer-related fatigue.
Cancer incidence: The rate of new cases of cancer, often reported per 100,000 people per year.
Cancer mortality: The cancer death rate, often reported as the number of deaths per 100,000 people per year.
Cancer of unknown primary (CUP): Metastatic cancer for which doctors cannot tell where in the body it started.
Cancer prevention: Action taken to lower the chance of getting cancer.
Cancer recurrence: The return of cancer after treatment; fear of recurrence is common and often lessens over time.
Cancer survivor: In cancer statistics, a person who is living after a cancer diagnosis.
Carcinogenesis: The process in which a normal cell becomes a cancer cell.
Carcinoma: The most common type of cancer, formed by epithelial cells that cover the inside and outside surfaces of the body.
Carcinoma in situ: An early condition, sometimes called stage 0, in which abnormal cells are present but have not invaded nearby tissue. It is not cancer but may become cancer.
Caregiver: A family member or friend who helps care for a person with cancer, through daily tasks, medical help, coordinating care, or emotional support.
Caregiver self-care: Taking care of your own needs, health, and feelings while caring for someone with cancer, so you have the strength to keep caring for others.
Catheter: A thin, soft tube placed in a large vein, often in the chest, used to give chemotherapy or other drugs and to draw blood.
Cell division: The process by which cells grow and multiply to form new cells as the body needs them.
Chemoprevention: The use of substances, natural or made in a laboratory, to lower the risk of cancer or keep it from coming back.
Chemotherapy: A type of cancer treatment that uses drugs to kill cancer cells or stop their growth. Also called chemo.
Chronic leukemia: A type of leukemia that grows slowly.
Chronic pain: Pain that usually lasts more than three months. Also called persistent pain; it may be mild or severe and may come and go or be constant.
Clinical trial: A research study that tests how well new medical approaches work in people.
Colon: Part of the large intestine, where colorectal cancer can form.
Complete blood count (CBC): A lab test that measures the numbers of red blood cells, white blood cells, and platelets in the blood, along with other details. It can help diagnose some cancers, especially leukemias.
Counselor: A professional such as a social worker, psychologist, or faith leader who can help you talk through feelings and learn ways to cope.
Cryosurgery: A treatment in which extreme cold, produced by liquid nitrogen or argon gas, is used to destroy abnormal tissue. Also called cryotherapy.
CT scan: An imaging test that uses an X-ray machine linked to a computer to take a series of pictures from different angles, creating detailed 3-D images of the inside of the body.
Cycle: In cancer treatment, a period of treatment followed by a period of rest that gives the body a chance to recover and build new healthy cells.
Cytokines: Naturally produced substances that help the body fight infections and cancer, but that can cause fatigue when released at high levels.
Debulk: To remove some, but not all, of a cancer tumor, often to help other treatments work better or to protect an organ.
Dehydration: A serious problem that happens when the body loses too much fluid, which can occur with vomiting when you are not drinking enough.
Depression: More than ordinary sadness—a medical condition in which painful feelings don't get better and get in the way of daily life. It can be treated.
Diagnostic test: A test done to find out whether cancer is present, often after an abnormal screening result. It may include a biopsy.
Distress: A high level of emotional suffering that can lead to physical problems such as fatigue, insomnia, and appetite loss.
DNA repair gene: A gene involved in fixing damaged DNA. Changes in these genes can let cells build up more changes that may make them cancerous.
Drug tolerance: A condition that happens when your body gets used to a medicine and it no longer works as well as it first did.
Ductal cancer: Breast cancer that starts in the ducts, the thin tubes that carry milk from the lobules to the nipple.
Dysplasia: A tissue change more advanced than hyperplasia, in which extra cells build up and look abnormal under a microscope. It is not cancer but may become cancer.
Dysplastic nevi: A kind of mole that is related to the risk of melanoma.
Early satiety: Feeling full after eating only a small amount of food.
Electrolytes: Minerals such as potassium, sodium, and calcium that help balance body fluids and support the heart, nerve, and muscle functions.
Eligibility criteria: The requirements that must be met for a person to join a clinical trial.
Endoscopy: A procedure in which a doctor inserts a thin, lighted tube called an endoscope into a natural body opening to look inside the body and, sometimes, remove a tissue sample.
Enteral nutrition: Nutrition support that gives nutrients in liquid form through a feeding tube placed into the stomach or small intestine.
Epidemiology study: A study that looks at large groups of people and compares those who develop a disease with those who don't, to find possible risk factors.
Exocrine cells: One of the two kinds of pancreas cells that pancreatic cancer can start in; cancer here is the more common type.
External beam radiation therapy: Radiation therapy that comes from a machine outside the body that aims radiation at the cancer. It treats a specific part of the body.
False-negative result: A test result that shows there is no cancer when there really is.
False-positive result: A test result that shows there is cancer when there really is not.
Fatigue: Feeling exhausted and worn out; the most common side effect of chemotherapy.
Fluid retention: A buildup of extra fluid in the body (also called edema) that can cause weight gain and swelling.
Follow-up care plan: A summary of your cancer treatment along with next steps for your care, which can give you a sense of control after treatment.
Frozen section: A rapidly prepared tissue sample used when an immediate answer is needed, such as during surgery. It can be examined in about 15 to 20 minutes.
Gene: A basic physical unit of inheritance that controls the way our cells function, especially how they grow and divide.
Graft-versus-host disease: A serious problem after a donor transplant in which white blood cells from the donor attack the recipient's cells as foreign.
Graft-versus-tumor: An effect after a donor transplant in which white blood cells from the donor attack any remaining cancer cells in the body.
Gross description: The part of a pathology report that describes the color, weight, size, and shape of a tissue sample as seen by the naked eye.
Healthy tissue: Normal cells and organs in the body that are not cancer but can be affected by cancer treatment.
HLAs: Human leukocyte antigens; sets of protein markers on most cells in the body, used to decide if a donor's stem cells are a match.
Hodgkin lymphoma: One of the two main types of lymphoma; it can often be cured.
Hormone therapy: A cancer treatment that slows or stops the growth of cancer that uses hormones to grow. Also called hormonal therapy or endocrine therapy.
Hormones: Substances made in the body that certain cancers, such as some breast and prostate cancers, use to grow.
Hyperplasia: A tissue change in which cells multiply faster than normal and extra cells build up, but the cells and tissue still look normal under a microscope. It is not cancer.
Imaging test: A test such as a CT scan, MRI, PET scan, ultrasound, or X-ray that creates pictures of areas inside the body.
Immune checkpoint inhibitors: Drugs that block immune checkpoints, which are a normal part of the immune system, so that immune cells can respond more strongly to cancer.
Immune system: The system that helps your body fight infections and other diseases, made up of white blood cells and the organs and tissues of the lymph system.
Immune system modulators: Agents that enhance the body's immune response against cancer, either in specific ways or more generally.
Immunotherapy: A type of cancer treatment that helps your immune system fight cancer.
Informed and shared decision-making: Deciding about a screening test together with your healthcare provider after learning its benefits and harms.
Informed consent: The process of learning the key facts about a clinical trial, including its risks and benefits, before deciding whether to take part.
Inherited cancer syndrome: A condition, sometimes suggested by a family history of certain cancers, caused by inherited genetic changes that can raise the risk of cancer.
Internal radiation therapy: Radiation therapy in which a source of radiation, solid or liquid, is placed inside the body.
Invasive cancer: Cancer that has spread into surrounding tissue and may spread to nearby lymph nodes or other organs.
Islet cells: A kind of neuroendocrine cell in the pancreas; tumors that start here are called islet cell tumors.
Jaundice: A yellowing of the skin and the whites of the eyes, which can be a skin-related symptom that cancer may cause.
Laparoscope: A long, thin tube with a tiny camera that is inserted through a small cut so the surgeon can see inside the body on a monitor.
Late effects: Side effects of cancer treatment that may not show up until months or years after treatment ends.
Leukemia: Cancer that begins in the blood-forming tissue of the bone marrow and does not form solid tumors; instead, abnormal white blood cells build up and crowd out normal blood cells.
Liquid biopsy: A test done on a sample of blood to look for cancer cells or pieces of DNA from tumor cells that are sometimes released into the blood.
Lobular cancer: Breast cancer that starts in the lobules, the tiny glands that make milk.
Local treatment: A treatment that treats only a specific part of the body, such as surgery or external beam radiation therapy.
Localized cancer: Cancer that is limited to the place where it started, with no sign that it has spread.
Long-distance caregiving: Giving support and coordinating care for a loved one who lives more than about an hour away, often by phone, email, or video.
Lymph node: A small, bean-shaped structure that filters lymph and stores white blood cells that help fight infection and disease.
Lymph system: The part of the body, including lymph nodes and vessels, where lymphoma begins.
Lymphatic system: A network of tissues and vessels that carries lymph fluid through the body. Cancer cells can travel through it to spread to other parts of the body.
Lymphoma: Cancer that begins in lymphocytes (T cells or B cells), which are disease-fighting white blood cells. The two main types are Hodgkin and non-Hodgkin lymphoma.
Malignant: Cancerous. Malignant tumors can invade nearby tissues and spread to distant parts of the body.
Malignant tumor: A cancerous tumor whose cells can invade nearby tissues and spread to other parts of the body.
Malnutrition: A condition in which the body doesn't get enough energy, protein, vitamins, and minerals.
Margin: The edge of the normal tissue removed around a tumor during surgery. A negative (clean) margin has no cancer cells at the edge; a positive (involved) margin has cancer cells at the edge.
Melanoma: Cancer that begins in cells that become melanocytes, the cells that make the pigment that gives skin its color. Most melanomas form on the skin.
Menopause: The time in a woman's life when her periods stop.
Metastasis: The process by which cancer cells spread from where they first formed to another part of the body.
Metastatic cancer: Cancer that has spread from where it first formed to a distant part of the body. For many cancer types it is also called stage 4 cancer.
Microscopic description: The part of a pathology report that describes how the cells and tissue look under the microscope after staining.
Minimally invasive surgery: Surgery in which the surgeon makes a few small cuts and uses a thin tube with a tiny camera (a laparoscope) to remove the tumor.
Monoclonal antibodies: Lab-made proteins, also called therapeutic antibodies, designed to attach to specific targets on cancer cells.
MRI: An imaging test that uses a powerful magnet and radio waves to take pictures of the body in slices, which can show places where there may be tumors.
Multiple myeloma: Cancer that begins in plasma cells, a type of immune cell, and builds up in the bone marrow.
Nausea: Feeling sick to your stomach, as if you have the urge to throw up.
Neoadjuvant chemotherapy: Chemotherapy given to make a tumor smaller before surgery or radiation therapy.
Neoadjuvant therapy: Treatment given to make a tumor smaller before surgery or radiation therapy.
Neuroendocrine cells: One of the two kinds of pancreas cells that pancreatic cancer can start in; islet cells are an example.
New normal: The adjusted way of life many people find after cancer treatment—not so much getting back to how things were as finding what is normal for them now.
Non-Hodgkin lymphoma (NHL): One of the two main types of lymphoma; its outlook depends on the specific type.
Non-small cell lung cancer: One of the two main types of lung cancer; it is the more common type.
Nutrition: What you eat and drink and how your body uses it; good nutrition is important for good health.
Open surgery: Surgery in which the surgeon makes one large cut to remove the tumor, some healthy tissue, and maybe some nearby lymph nodes.
Opioids: Strong prescription pain medicines, also called narcotics, used for moderate to severe cancer pain.
Overdiagnosis: The detection of cancers, often through screening, that would not have caused a problem during a person's life.
Palliative care: Care that improves quality of life by relieving symptoms of cancer and side effects of treatment. It can be given at any point during cancer treatment.
Palliative care specialist: A health professional who focuses on relieving symptoms such as pain and may lead a pain control team.
Palliative treatment: Treatment used to ease symptoms rather than cure the cancer.
Parenteral nutrition: Nutrition support that gives nutrients directly into the blood through a catheter in a vein, used when you cannot take food by mouth or use a feeding tube.
Pathologist: A doctor who has special training in identifying diseases by studying cells and tissues under a microscope.
Pathology report: A medical report written by a pathologist that describes the characteristics of a tissue sample and provides the definitive cancer diagnosis.
Peripheral blood stem cell transplant: A stem cell transplant in which the blood-forming stem cells come from the bloodstream.
PET scan: A type of nuclear scan that shows areas inside the body where glucose is taken up. Because cancer cells often take up more glucose, the pictures can help find cancer.
Phase (of a clinical trial): One of the series of steps used to test a new cancer treatment, from phase 1 through phase 4.
Physical dependence: A condition in which the body gets used to a drug and has unpleasant symptoms if the drug is suddenly stopped or greatly reduced. It is not the same as addiction.
Placebo: An inactive substance sometimes used in trials for comparison; it is rarely used in cancer treatment trials.
Polyp: A growth inside the colon or rectum. Colorectal cancer often begins as a polyp.
Port: A small, round disc placed under the skin during minor surgery and connected by a catheter to a large vein, used to give chemotherapy or draw blood.
Precancerous condition: A condition that may become cancer.
Precision medicine: An approach to treatment in which drugs are designed to target the specific proteins and DNA changes that drive a person's cancer.
Prevention trial: A clinical trial that looks at ways to prevent cancer, often in people at high risk.
Primary cancer: The original cancer, in the place where it first formed.
Primary tumor: The main, original tumor where the cancer first started.
Prognosis: The likely course and outcome of a disease.
Prostate-specific antigen (PSA) test: A test that is one tool related to prostate cancer screening.
Protective factor: Something that is linked to a lower risk of developing cancer.
Proto-oncogene: A gene involved in normal cell growth and division that, when altered or overactive, may become a cancer-causing gene (an oncogene).
PSA: Prostate-specific antigen; a substance measured by a blood test used to help tell whether hormone therapy for prostate cancer is working.
Radiation therapy: A cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. Also called radiotherapy.
Randomization: Assigning people by chance to different treatment groups in a trial, which helps prevent bias.
Rectum: The lower part of the large intestine, where colorectal cancer can form.
Regional cancer: Cancer that has spread to nearby lymph nodes, tissues, or organs.
Registered dietitian: A nutrition expert who can assess your needs and create a nutrition care plan to help you eat well before, during, and after treatment.
Risk factor: Something that increases a person's chance of developing a disease such as cancer. Some risk factors can be avoided and others cannot.
Sarcoma: Cancer that forms in bone and soft tissues, including muscle, fat, blood vessels, lymph vessels, and fibrous tissue such as tendons and ligaments.
Screening: Looking for cancer, or for abnormal cells that may become cancer, in people who have no symptoms.
Screening trial: A clinical trial that tests ways to find cancer before it causes symptoms.
SEER Program: The National Cancer Institute's Surveillance, Epidemiology, and End Results Program, which collects and publishes cancer incidence and survival data covering about 48% of the U.S. population.
Sentinel lymph nodes: The first nearby lymph nodes that a surgeon may remove, especially in breast cancer and melanoma, so a pathologist can check whether they contain cancer cells.
Side effect: A problem that occurs when treatment affects healthy tissues or organs, not just the cancer.
Skin cancer: The most common type of cancer. Its main types are squamous cell carcinoma, basal cell carcinoma, and melanoma.
Small cell lung cancer: One of the two main types of lung cancer.
Small-molecule drugs: Targeted therapy drugs small enough to enter cells easily, used for targets inside cells.
Stage: The extent of a cancer, such as how large the tumor is and whether it has spread.
Standard treatment: The treatment currently used and accepted as the usual approach for a condition.
Stem cell transplant: A procedure that restores blood-forming stem cells in people who have had theirs destroyed by high doses of chemotherapy or radiation therapy.
Support group: A group where people with cancer or their caregivers share feelings, trade advice, and support one another, meeting in person, by phone, or online.
Supportive care trial: A clinical trial that looks at ways to improve the quality of life of people with cancer, especially side effects.
Surgery: When used to treat cancer, a procedure in which a surgeon removes cancer from the body. It works best for solid tumors contained in one area.
Symptom: A sign or feeling of illness that a person notices, such as a lump, fatigue, or bleeding. Cancer can cause many symptoms, though they are most often caused by other problems.
Syngeneic transplant: A transplant in which the stem cells come from your identical twin.
Systemic radiation therapy: Internal radiation therapy with a liquid source that travels in the blood to tissues throughout the body.
T-cell transfer therapy: A treatment that boosts the natural ability of your T cells to fight cancer. Also called adoptive cell therapy.
Targeted therapy: A type of cancer treatment that targets proteins that control how cancer cells grow, divide, and spread.
TNM staging system: The most widely used cancer staging system. T describes the main tumor, N describes nearby lymph nodes with cancer, and M describes whether the cancer has spread (metastasized).
Treatment trial: A clinical trial that tests new treatments or new ways of using existing treatments in people who have cancer.
Treatment vaccines: Vaccines that work against cancer by boosting your immune system's response to cancer cells; different from vaccines that prevent disease.
Tumor: A lump of tissue that forms when cells grow and multiply when they shouldn't. Tumors can be cancerous or not cancerous.
Tumor marker: A substance produced by cancer cells or by other cells of the body in response to cancer. Most are made by both normal and cancer cells but at much higher levels by cancer cells.
Tumor suppressor gene: A gene involved in controlling cell growth and division. Certain changes in these genes can allow cells to divide in an uncontrolled way.
UV radiation: Ultraviolet radiation from the sun, sunlamps, and tanning booths that causes damage that can lead to skin cancer.
Vomiting: Throwing up the contents of the stomach.

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