Cancer Terms (Terminology)

Receiving a cancer diagnosis is an emotional shock. The first step in understanding your situation is mastering the terminology used in the cancer world.
Each type of cancer has its own unique set of terms but the list below, courtesy of, is a basic list of terms common to all cancers.
Absolute risk
The difference between two risks, usually smaller than relative risk.
Refers to symptoms that start and worsen quickly but do not last over a long time.
Adjuvant therapy
Treatment given after the main treatment to reduce the chance of cancer coming back by destroying any remaining cancer cells. It usually refers to chemotherapy, radiation therapy, hormone therapy, and/or immunotherapy given after surgery.
Americans with Disabilities Act (ADA)
Associated costs
The middle value of a set of numbers, calculated by adding all of the values and dividing by the number of values in the set.
Bone marrow
Bone marrow transplant
A medical procedure in which diseased bone marrow is replaced by healthy bone marrow from a volunteer donor. Learn more about bone marrow transplantation.
A group of more than 100 different diseases that can begin almost anywhere in the body, characterized by abnormal cell growth and the ability to invade nearby tissues. Learn more about the basics of cancer.
Case manager
The basic units that make up the human body.
Refers to a disease or condition that persists, often slowly, over a long time.
Clinical significance
Clinical trial
A research study that tests new treatments and/or prevention methods to find out whether they are safe, effective, and possibly better than the current standard of care (the best-known treatment). Learn more about clinical trials.
The percentage of health care costs an insured patient pays after meeting a health care plan’s yearly deductible. For example, an 80/20 co-insurance rate means that the insurance company pays 80% of approved health care costs, and the patient pays the remaining 20% of costs out-of-pocket.
A set fee, in dollars, that an insurance provider requires a patient to pay each time care is received. For example, a visit to the oncologist may cost a patient $30 each time; the insurance provider pays the rest of the visit’s costs. The amount of the co-pay is set by the insurance provider, not the doctor’s office.
A group of individuals who share a common experience, exposure, or trait and who are under observation in a research study.
Complementary medicine
A diverse group of treatments, techniques, and products that are used in addition to standard cancer treatments. Learn more about types of complementary therapies.
Confidence interval
Confounding variable
A factor in a scientific study that wasn’t addressed that could affect the outcome of the study, such as smoking history in a study of people with cancer.
Control group
Disability insurance
Disease-free survival (DFS)
The results measured at the end of a study to see whether the research question was answered.
Essential health benefits
Event-free survival (EFS)
Family and Medical Leave Act (FMLA)
Follow-up care
Medical examinations and tests the doctor recommends after the active treatment period. This care is used to monitor a patient’s recovery and check for signs of recurrence.
Health Insurance Portability and Accountability Act. This is a set of national rules that help protect the privacy of a patient’s personal medical information, provide patients with access to their medical records, and help people with health problems, such as cancer, get health insurance for themselves and their family members. Learn more from the U.S. Department of Health and Human Services.
Hormone therapy
Imaging test
A procedure that creates pictures of internal body parts, tissues, or organs to make a diagnosis, plan treatment, find out whether treatment is working, or observe a disease over time.
In situ
In place. Refers to cancer that has not spread to nearby tissue, also called non-invasive cancer.
In-network care
Health care providers or facilities that are part of an HMO or PPO plan’s approved list or network are considered “in network.” In general, in-network care costs patients less than out-of-network care.
The number of new instances of a disease or condition in a particular population during a specific period. Learn more about statistics used to estimate risk and recommend screening.
Insurance cap
The amount of money an insurance plan will pay in total benefits. Once a patient’s medical bills reach the total, or cap, the plan will no longer provide coverage. Both lifetime and annual caps were eliminated under the Affordable Care Act. For more information read the section summarizing this law or visit
Integrative medicine
A combination of medical treatments for cancer and complementary therapies to help manage the symptoms and side effects of cancer. Learn more about integrative medicine.
Invasive cancer
Cancer that has spread outside the layer of tissue in which it started and has the potential to grow into other tissues or parts of the body, also called infiltrating cancer.
Laboratory test
Late effects
Side effects of cancer treatment that occur months or years after a diagnosis of cancer because of the related treatments, such as chemotherapy, radiation therapy, or surgery. Learn more about the long-term side effects of cancer treatment.
Lifetime risk
The probability of developing a disease or dying from that disease across a person’s lifetime.
Localized cancer
Long-term care insurance
Insurance that helps people with long-lasting illnesses or disabilities pay for non-medical daily services and care that ordinary health plans don’t cover, such as help with eating, bathing, and dressing. Depending on the plan, care can be given in the home or outside the home.
Lymphatic system
A cancer of the lymphatic system. Lymphoma begins when cells in the lymph system change and grow uncontrollably. Sometimes a tumor is formed.
A lump in the body.
The middle value in a range of measurements ordered by value.
The spread of cancer from the place where the cancer began to another part of the body. Cancer cells can break away from the primary tumor and travel through the blood or the lymphatic system to the lymph nodes, brain, lungs, bones, liver, or other organs.
Mortality rate
The number of deaths in a particular population during a specific time.
Neoadjuvant therapy
Treatment given before the main treatment. It may include chemotherapy, radiation therapy, or hormone therapy given before surgery to shrink a tumor so that it is easier to remove.
Non-essential benefits
Odds ratio
A comparison of whether the likelihood of an event is similar between two groups; a ratio of 1 means it is equally likely between both groups.
A doctor who treats cancer and provides medical care for a person diagnosed with cancer. The five main types of oncologists are medical, surgical, radiation, gynecologic, and pediatric oncologists. Learn more about the types of oncologists.
The study of cancer.
Oncology Nurse
A nurse who specializes in caring for people with cancer.
Open enrollment
Out-of-network care
Health care providers or facilities that are not part of an HMO or PPO plan’s approved list or network are considered “out of network.” Out-of-network care often costs patients more than in-network care and may involve a deductible and require pre-approval for certain services.
Out-of-pocket costs
Any expense not covered by insurance that a patient must pay.
A measurable result or effect.
Palliative care
Palliative care is any form of treatment that concentrates on reducing a patient’s symptoms or treatment side effects, improving quality of life, and supporting patients and their families. It may also be called supportive care. Learn more about palliative care.
Patient navigator
Patient Protection and Affordable Care Act
An inactive drug or treatment in a clinical trial. Find out more about the current use of placebos in cancer clinical trials.
Power of attorney (POA), financial
A legal document that allows a person to select another person to act on their behalf on financial matters. Learn more about a power of attorney.
Pre-existing condition
A tendency to develop a disease that can be triggered under certain conditions. For example, although a genetic predisposition to cancer increases a person’s risk of developing cancer, it is not certain that the person will develop it. Learn more about genetics.
Primary cancer
Describes the original cancer.
Progression-free survival (PFS)
The length of time during and after treatment that the cancer does not grow or spread further. This term is often used in the context of scientific research.
A formal, written action plan for how a clinical trial will be carried out. It states the goals and timeline of the study, who is eligible to participate, what treatments and tests will be given, how often, and what information will be gathered.
Radiation therapy
The use of high-energy x-rays or other particles to destroy cancer cells. The most common type of radiation treatment is called external-beam radiation therapy, which is radiation given from a machine outside the body. When radiation treatment is given using implants near the cancer cells, it is called internal radiation therapy or brachytherapy. Learn more about radiation therapy.
Reasonable and customary fees
The average cost for health services in a geographic area that insurance plans use to decide how much they will pay for those services. If a doctor’s fees for a service are higher than average, the patient must pay the difference.
Cancer that has returned after a period during which the cancer could not be detected. “Local recurrence” means that the cancer has come back to the same general area where the original cancer was located. “Regional recurrence” refers to cancer that has come back in the lymph nodes or other tissues near the original cancer site, usually by direct spread. “Distant recurrence” refers to cancer that has come back and has spread to other parts of the body, usually by traveling through the lymph system or bloodstream. Learn more about dealing with cancer recurrence.
Services and resources that help a person with cancer obtain the best physical, social, psychological, and work-related functioning during and after cancer treatment. Find out more about rehabilitation.
Relative risk
Compares the risk of disease between two groups of people.
Relative survival
The amount of time after treatment that a person with cancer lives, excluding all other causes of death but cancer. Learn more about survival statistics.
Secondary cancer
Social Security Disability Insurance and Supplemental Security Income
Social worker
Specialist care
A way of describing cancer, such as where it is located, whether or where it has spread, and whether it is affecting the functions of other organs in the body. Learn more about the stages of cancer.
Standard of care
Care that experts agree or guidelines show is the most appropriate and/or effective for a specific type and stage of cancer.
The removal of cancerous tissue from the body through an operation. Learn more about cancer surgery.
This term means different things to different people. Two common definitions include having no disease after the completion of treatment and the process of living with, through, and beyond cancer. Learn more about cancer survivorship.
Survivorship care plan
A personalized schedule of follow-up examinations and tests that the doctor recommends after a patient’s active treatment period ends. This may include regular physical examinations and/or medical tests to monitor the patient’s recovery for the coming months and years. It may also be called a follow-up care plan; it is often used in conjunction with a treatment summary (see below). Develop a survivorship care plan with your doctor using ASCO forms.
Targeted therapy
Treatment that targets specific genes, proteins, or other molecules that contribute to cancer growth and survival. Learn more about targeted therapy.
Treatment Summary
A mass formed when normal cells begin to change and grow uncontrollably. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body). Also called a nodule or mass.