Carcinoma of Unknown Primary

Despite the sophisticated diagnostic tools available to establish the diagnosis of human neoplasia, oncologists frequently are asked to evaluate and treat a subset of patients with metastatic cancer in whom detailed investigations fail to identify a primary anatomic site. The reported prevalence of unknown primary carcinoma (UPC) varies with the practice setting and the definition used from 0.5% to 9% of all patients who are diagnosed with cancer [1,2]. Because identification of the primary has formed the basis for predicting the expected behavior and assigning appropriate therapy of malignant diseases, the absence of a primary poses a major challenge. The inability to identify a primary generates anxiety for the patient, who may believe that the physician’s evaluation has been inadequate or that the prognosis would be improved if a primary could be established.