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.

DCIS
A noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues. At this time, there is no way to know which lesions could become invasive. Also called ductal carcinoma in situ and intraductal carcinoma.

EnlargeDuctal carcinoma in situ (DCIS); drawing shows  a lobe, ducts, and fatty tissue in a cross section of the breast. The inset shows a normal duct and a duct with abnormal cells.

Ductal carcinoma in situ (DCIS). Abnormal cells are found in the lining of a breast duct.