Unknow Primary Ca

This document summarizes an article on cancer of unknown primary origin (CUP). CUP represents about 3% of cancer cases where patients present with metastatic disease but the primary site cannot be identified. Histologically, CUP is usually adenocarcinoma but can also be poorly differentiated carcinoma, squamous cell carcinoma, or other subtypes. Prognosis is generally poor with a median survival of 5-10 months, though some subgroups like women with axillary node involvement only have better outcomes. The document discusses diagnostic approaches and treatment considerations for CUP.