NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,856 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.

melanoma in situ
(MEH-luh-NOH-muh in SY-too)
Abnormal melanocytes (cells that make melanin, the pigment that gives skin its color) are found in the epidermis (outer layer of the skin). These abnormal melanocytes may become cancer and spread into nearby normal tissue. Also called stage 0 melanoma.