Cancer of Unknown Primary (CUP)
Cancer of Unknown Primary (CUP)
Patient Information
Oncology Services
- Author ID: UM
- Leaflet ref: CC 040
- Version: 7
- Date Produced: April 2025
- Expiry Date: April 2027
What is cancer of unknown primary?
Cancer of unknown primary is a term used when a cancer has been diagnosed but the original (or primary) place where the cancer started cannot be found. Approximately 3 to 5% of cancer diagnoses are cancers of unknown primary (CUP).
In patients with CUP, symptoms are caused by a cancer that has spread. This is called a secondary cancer. Despite usual tests the primary site of the cancer cannot be identified.
Why can’t the primary cancer be found?
There are different reasons why the primary cancer cannot be found:
- It may be too small to be seen on a scan or be hidden beside a larger secondary cancer
- It might have disappeared, even though it has spread to other parts of the body
- Your immune system may have destroyed the primary cancer but not the secondary sites
Investigations
When a new tumour is found it is not always obvious what type of cancer it is, so further tests and investigations need to be done to try to find out. In CUP, this process can take longer as more tests may be needed to try to find out where the cancer came from.
What tests will be done?
This will vary for every person but often includes the following:
- Blood tests: to detect substances in your blood called tumour markers which are made by some cancers
- Biopsy: a small piece of tissue will be taken from a tumour using a needle. This is one of the most important tests and can help show what type of cancer you have
- Chest X-ray and sometimes X-rays of other areas of your body
- Imaging scans – computed tomography (CT) scans, magnetic resonance (MR) imaging scans or positron emission tomography (PET) scans: may be requested by your doctor
Even when tests have not found where the cancer started, they can still give useful information to help doctors decide on the most appropriate treatment for you. If the results of tests are not likely to affect which treatment you are offered, this will be discussed with you.
You may like to have someone from your family or a close friend with you during these discussions.
You may decide that you do not want to have treatment, in which case you will not be offered further tests.
You may be offered palliative care; this aims to control your symptoms and help you to keep your quality of life. You may also be referred to the Community Palliative Care Team for support when you leave hospital.
What is the treatment for cancer of unknown primary?
The most common treatment for CUP is chemotherapy. Chemotherapy is a systemic treatment, which means it treats cancer in more than one area of the body.
Supportive or palliative care with medicines to control your symptoms can be an important part of treatment for people with CUP. Sometimes doctors advise palliative care on its own rather than treating the cancer. This may be because the cancer is very advanced, and the disadvantages of treatment outweigh the advantages.
Key worker
If you are diagnosed with CUP, you will be referred to the Acute Oncology Service and allocated a key worker to help support you. This will usually be a specialist nurse.
Your key worker will help co-ordinate your care and will try to help answer your questions, address your concerns and support you through this difficult time.
Your key worker is
……………………………………………………………………………
Macmillan Acute Oncology Nurse Specialist
Royal Albert Edward infirmary
Main Tel: 0300 707 2710
Alternative Numbers
0300 707 2720 / 2532 / 3541
Monday to Friday 8 am to 5pm
Answerphone is available out of hours on 0300 707 2710
Supportive and Palliative Care Team
Royal Albert Edward Infirmary
Wigan Lane
Wigan
WN1 2NN
0300 707 2008
Where can I find out more?
Macmillan Cancer Information & Support Centre
Cancer Care Centre
Wigan Lane
Wigan
0300 707 2760
The information centre is based in the new Cancer Care Centre at the Royal Albert Edward Infirmary. It is staffed by Macmillan information and support specialists who offer information, counselling, and practical support. They can also signpost patients; carers and loved ones to other services in the area such as support groups.
Further Macmillan information points can be found at:
- Thomas Linacre Centre (ground floor)
- Leigh Infirmary
Useful websites
Last modified 22nd September 2026 10:37:01 am