(i.e., tends to increase or decrease) an observed difference in the outcomes of a treatment group and a control group.


—use of computers and specialized software to organize and analyze biological information and data.


—A substance sometimes found in the blood, other body fluids, or tissues. A high level of biomarker may mean that a certain type of cancer is in the body. Examples of biomarkers include CA 125 (ovarian cancer), CA 15-3 (breast cancer), CEA (ovarian, lung, breast, pancreatic, and gastrointestinal tract cancers), and PSA (prostate cancer). See also Tumor marker.


—refers to a procedure that involves obtaining a tissue specimen for microscopic analysis to establish a diagnosis; 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.


—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.


—a gene located on chromosome 13; a germ-line mutation in this gene is associated with increased risk of breast cancer.

Breast self-examination

—monthly physical examination of the breasts with the intent of finding lumps that could be an early indication of cancer.


—a general term for more than 100 diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread through the bloodstream and lymphatic system to other parts of the body. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is 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 bloodstream. Lymphoma is cancer that begins in the cells of the immune system.


—any substance or agent that produces or incites cancer.

Carcinoma in situ

—Cancer that involves only the cells in which it began and that has not spread to nearby tissues.

Case-control study

—a study that compares two groups of people—those with the disease or condition under study (cases) and a very similar group of people who do not have the disease or condition (controls). Researchers study the medical and lifestyle histories of the people in each group to learn what factors may be associated with the disease or condition. For example, one group may have been exposed to a

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