The actual tumor origin is the most important thing in planning treatment and assessing the prognosis . By definition, all CUPS are in an advanced stage because the cancer has already metastasized. It has been suggested that doctors caring for patients with CUPS should refrain from extensive investigations, since the time and discomfort involved are not worth the results and may not affect survival anyway.
The results of exhaustive tests are also sometimes misleading. The tests may sometimes seem to show a positive finding when none is really there (false positive) or may instead fail to show an abnormality that is present but not detectable (false negative).
