Table 1.

Terms used in NICE guideline to define CUP

MUO	Metastatic malignancy identified on the basis of a limited number of tests, without an obvious primary site, before comprehensive investigation
Provisional CUP origin	Metastatic epithelial or neuroendocrine malignancy identified on the basis of the histology or cytology, with no primary site detected despite a selected initial screen of investigations, before specialist review and possible further specialised investigations
Confirmed CUP origin	Metastatic epithelial or neuroendocrine malignancy identified on the basis of final histology, with no primary site detected despite a selected initial screen of investigations, specialist review and further specialised investigations as appropriate

CUP, cancer of unknown primary; MUO, malignancy of undefined primary origin; NICE, National Institute of Clinical Excellence.