Cancer of unknown primary (CUP)

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. Cancer can spread from this primary to other parts of the body, these are called secondary cancers, and commonly known as metastases.

Cancer of unknown primary (CUP) is when a secondary cancer is diagnosed, but despite tests the doctors can’t identify where the cancer first started. The primary cancer is unknown.

There are doctors and nurses that specialise in (CUP) if the primary cannot be found. The specialists will look at all the test results, your symptoms, and where the secondary cancers are to suggest the most likely part of the body where the primary cancer started.
From here the specialists can discuss and advise what potential treatments may be helpful

Cancer of unknown primary is the 15th most common cancer in the UK, accounting for 2% of all new cancer cases (2016-2018). Cancer research UK.

Meet the Cancer of Unknown Primary team.

Am I at risk?

Doctors cannot be sure the exact risk of (CUP) because they don’t know exactly where the cancer started.

CUP is more common in older people. In the UK, almost 60 out of 100 people (almost 60%) diagnosed with CUP are 75 and over.

Why can the primary cancer not be found?

There are different reasons why doctors can’t find a primary site of cancer. They don’t always know for certain why or how this happens.

This may be because;

  • it is too small to be seen on scans
  • it is hidden beside or behind a larger secondary cancer
  • the body’s immune system has destroyed the original primary cancer and it has disappeared, but the secondary cancer is still growing

Symptoms of cancer of unknown primary

Symptoms of CUP depend on where the cancer has spread to in your body. Possible symptoms of CUP include:

  • weight loss
  • sickness and loss of appetite
  • weakness or feeling very tired
  • pain in your bones, or your abdomen
  • breathlessness
  • a cough that won’t go away
  • swollen lymph nodes

All the symptoms mentioned here can be caused by conditions other than cancer. But it is important to see your GP and get them checked.

Patient information

For more information from Macmillan regarding cancer of unknown primary, please follow this link.

For more information from Cancer Research UK regarding cancer of unknown primary, please follow this link.