Home > Encyclopedia of Cancer > Carcinoma of Unknown Primary

Definition

Carcinoma of unknown primary (CUP) is a disease in which malignant (cancerous) cells are found in the body, but the organ where they initially began growing, the primary site, cannot be discovered.

Description

The area where a cancer originates in the body is often referred to as the primary tumor. Cancer of unknown primary is a cancer that starts out in an unknown spot and then metastasizes (spreads) to another site, such as a lymph node, the liver, lung, brain, or the bones. Because the primary site is unknown, prognosis may differ from patient to patient.

Most cancers are named after the area of the body in which...