How to Diagnose and Treat a Cancer of Unknown Primary Site

Almost one in every three patients with advanced tumors have distant metastasis at the time of clinical diagnosis. In most cases, the primary tumor site is identified immediately, within a few days. But for some patients, the primary lesion cannot be found after the initial clinical assessment. These cases are called cancers of unknown primary origin (CUPs), a clinical diagnosis very difficult to manage by physicians due to the absence of a standard-of-care for the initial therapeutic regimen, as well as due to the impossibility to include these cases in randomized clinical trials. A cancer of unknown primary site is often associated with a poor prognosis as patients are usually treated with a non-selective empirical therapy. In the current paper, we summarize both the diagnostic challenges for patients with a cancer of unknown primary site as well as the current available therapeutic options, with emphasis on the management of this unique disease entity.