People with CUP have a malignancy that has already spread; therefore, by definition it is a metastatic cancer. There is no definite staging classification used for patients with CUP; however, disease can be classified as localised or disseminated disease.

CUP is a very heterogeneous disease. There is a specific CUP subset of patients who have a pattern of disease similar to known cancers types that may respond well to standard disease-specific treatment. The remaining patients are considered within the non-specific subset of CUP, with their prognosis and suitability for treatment dependent on their ECOG performance status and LDH level.

Between 2010 and 2014, people with CUP had a 14 per cent chance of surviving for five years when compared with the age- and sex-matched general Australian population (AIHW 2018).