Detecting undetectable - epidemiology, etiology, and diagnosis of carcinoma of unknown primary - systematic review.

Carcinoma of unknown primary (CUP) is a heterogeneous group of oncological diseases in which it is impossible to determine the primary tumor. The incidence is 3-5% of oncologic patients, but the survival time varies from 6 weeks to 5 months. The diagnostics should begin with a clinical evaluation and basic laboratory tests.