What are the key statistics about cancers of unknown primary?
The exact number of cancers of unknown primary (CUP) diagnosed each year is unknown, because some cancers start out being diagnosed as unknown primary, but the primary site is found later. Still, the American Cancer Society estimates that about 31,430 cases of cancer of unknown primary will be diagnosed in 2014 in the United States. This number represents less than 2% of all cancers. As more sophisticated lab tests become available to determine where a cancer started, the number of cancers of unknown primary may go down.
Last Medical Review: 03/12/2013
Last Revised: 01/31/2014