Metastatic malignant disease of unknown primary origin in adults: diagnosis and management

Cancer of unknown primary

When some of the cells in an organ or tissue of the body start to grow in an uncontrolled way, a cancer forms. The organ or tissue where the cancer first starts to grow is known as the primary cancer. But cancer can spread from this primary site to other parts of the body. When cancer spreads it forms secondary cancers (also known as metastases). Commonly affected areas include the liver, the lungs or the bones, but other areas may be affected too.

In most people the primary cancer is easily found with tests such as blood tests, X-rays and scans. But even after tests, sometimes it is not possible to tell where the cancer has come from. This is known as 'cancer of unknown primary'.

There are many different types of cancer of unknown primary and many possible treatments. Because of this, diagnosis may not be quick or straightforward. Healthcare professionals will usually want to try and find out as much as they can about where the cancer has come from to make treatment as effective as possible.