NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,812 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.

CUP
A case in which cancer cells are found in the body, but the place where the cells first started growing (the origin or primary site) cannot be determined. Also called cancer of unknown primary origin and carcinoma of unknown primary.

EnlargeCarcinoma of unknown primary; drawing shows a primary tumor that has spread from an unknown site to other parts of the body (the lung and the brain). An inset shows cancer cells spreading from the primary cancer, through the blood and lymph systems, to another part of the body where a metastatic tumor has formed.

In carcinoma of unknown primary, cancer cells have spread in the body but the place where the primary cancer began is unknown.