Occult primary.

Overview Occult primary tumors, or cancers of unknown primary (CUPs), are defined as histologically proven metastatic malignant tumors whose primary site cannot be identified during pretreatment evaluation.1,2 They have a wide variety of clinical presentations and a poor prognosis in most patients. Patients with occult primary tumors often present with general complaints, such as anorexia and weight loss. Clinical absence of primary tumor, early dissemination, aggressiveness, and unpredictability of metastatic pattern are characteristic of these tumors.3 Life expectancy is very short, with a median survival of 6 to 9 months.4 In most patients, occult primary tumors are refractory to systemic treatments, and chemotherapy NCCN