NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,777 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.

primary tumor
(PRY-mayr-ee TOO-mer)
A term used to describe the original, or first, tumor in the body. Cancer cells from a primary tumor may spread to other parts of the body and form new, or secondary, tumors. This is called metastasis. These secondary tumors are the same type of cancer as the primary tumor. Also called primary cancer.