Cancer terms may sometimes be difficult to understand. You may hear your doctor use certain medical terms, and you may not know what they mean. It is important to understand these terms, so you can make the best informed decision about your cancer treatment.

This is the first in a four-part series of articles designed to help people with cancer understand commonly used medical terms. The articles will address terms used throughout the cancer experience, from a new diagnosis to during and after treatment. The following article defines basic oncology terms, including those used in the detection of cancer.

Antibodies: Proteins in the immune system that recognize and attach to foreign molecules, called antigens.

Benign: A tumor that is not cancerous. The tumor does not invade nearby tissue or spread to other parts of the body.

Biopsy: Removal of a tissue sample that is then examined under a microscope to check for cancer cells.

Carcinoma: Cancer that starts in skin or tissues that line the inside or cover the outside of internal organs.

Chemotherapy: Drugs used to destroy cancer cells by interfering with their growth and/or preventing their reproduction.

Chromosome: A microscopic structure in the nucleus of a cell that contains genes.

Clinical trial: Research studies that test new treatment and prevention methods to find out if they are safe, effective, and better than the current standard of care (the best known treatment).

DNA (deoxyribonucleic acid): The molecules inside cells that store genetic information.

Endpoint: The results measured at the end of a study to see if a given treatment has worked.

Epidemiology: The study of the patterns, causes, and control of disease in groups of people. The study of cancer may involve looking at how many people have cancer; who develops specific types of cancer; and what factors, such as genetics or personal behavior, play a role in the development of cancer.

Gene: A length of DNA that carries the genetic information necessary for production of a protein. Genes are located on chromosomes and are the basic units of heredity.

Genetic testing: The analysis of a person’s DNA to check for genetic mutations (changes) that carry an increased risk of or predisposition to cancer.

Hormone: A substance produced by an organ or gland that is carried by the blood and produces a specific effect on other organs or glands.

Malignant: A tumor that is cancerous. The tumor may invade nearby healthy tissue or spread to other parts of the body.

Metastasis: The spread of cancer from 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.

Oncogene: A normal gene that when mutated plays a significant role in causing cancer.

Palliative: Treatment of the physical, spiritual, psychological, and social needs of a person with cancer. Its purpose is to improve quality of life.

Precancerous: Changes in cells that may, but do not always, become cancer. Also called pre-malignant.

Predisposition: A tendency to develop a disease that can be triggered under certain conditions. Although a predisposition to cancer increases a person's risk of developing cancer, it is not certain that the person will develop it.

Remission: The disappearance of the signs and symptoms of cancer, but not necessarily the entire disease. The disappearance can be temporary or permanent. Complete remission means all known tumors have disappeared. Partial remission refers to a greater than 50% reduction of tumor mass.

Additional resources

National Cancer Institute—Dictionary of Cancer Terms

American Cancer Society—Glossary

Stedman's Medical Dictionary

More Information

Read more articles in this four-part series.

Part II: Cancer Terms to Know: Newly Diagnosed

Part III: Cancer Terms to Know: During Treatment

Part IV: Cancer Terms to Know: After Treatment

Medical Dictionary Resources

Last Updated: October 16, 2006