NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,804 terms related to cancer and medicine.

Browse the dictionary by selecting a letter of the alphabet or by entering a cancer-related word or phrase in the search box.

guaiac smear test
(GWY-ak smeer …)
A test that checks for occult (hidden) blood in the stool. Small samples of stool are placed on special cards coated with a chemical substance called guaiac and sent to a doctor or laboratory for testing. A testing solution is put on the cards and the guaiac causes the stool sample to change color. If there is blood in the stool, the color changes very quickly. Blood in the stool may be a sign of colorectal cancer or other problems, such as polyps, ulcers, or hemorrhoids. Also called gFOBT, guaiac fecal occult blood test, and stool guaiac test.