Carcinoma of Unknown Primary (CUP)

Patient Experience

  • Reference Number: HEY-752/2023
  • Departments: Oncology (Cancer Services)
  • Last Updated: 29 August 2023


This leaflet has been produced to give you general information about your condition.  Most of your questions should be answered by this leaflet.  It is not intended to replace the discussion between you and your doctor but may act as a starting point for discussion.   If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team caring for you.

What is cancer of unknown primary (CUP)?

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.

Cancer of unknown primary can be referred to in different ways:

  • Cancer of Unknown Primary
  • Metastatic Malignancy of Unknown Origin
  • Carcinoma of Unknown Primary

Approximately 3% to 5% of cancer diagnoses are cancers of unknown primary.

In patients with CUP, symptoms are caused by a cancer that has spread. This is called a secondary cancer. Despite usual tests, the original site of the cancer cannot be identified.

Why can the primary cancer not 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. This is usually as a result of the primary cancer having lost its blood supply.
  • Your immune system (a system to help the body fight off infection) may have destroyed the primary cancer but not the secondary sites.

Investigations for CUP

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 and will be decided by your treating clinician in discussion with you. The tests often include the following:

  • Scans – CT scans, MRI scans or PET scans: These may be requested by your doctor.
  • 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. It may not however, be always possible to biopsy the tumour if it is in a difficult area of the body to reach; or if the risks of biopsy outweigh the benefits. Your doctor will discuss this with you if it is the case.
  • Chest X-ray: It may be that additional X-rays of other areas of your body are required.
  • Blood tests: These detect substances in your blood called tumour markers, which are made by some cancers.

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.

The CUP Multi-disciplinary Team (MDT)

Following your presentation to the hospital, or following a referral from your GP, your investigations will be discussed in a meeting attended by a number of specialists.  This is called an MDT meeting. The people involved in this decision-making process include:

  • an oncologist (a cancer doctor)
  • a palliative care physician (specialising in symptom control)
  • a radiologist (reads the scans and X-rays)
  • a pathologist (interprets any biopsy that you may have had done)
  • a cancer nurse specialist (who is going to be your key worker)
  • an administrator (who ensures that all your information is available to the team).

The team meets once a week and will discuss all relevant investigations that you have had done.  They will take into account your current physical state and your wishes.  The team will then recommend the best possible way of investigating you further, or any treatment that you are likely to benefit from. This decision will be discussed with you by your oncologist, or the palliative care physician, or the cancer nurse specialist at the next clinic that you will be attending.

What is the treatment for CUP?

CUP can be treated by chemotherapy, radiotherapy, hormone based medicines or a combination of all, depending on the type of cancer; the areas of spread and the physical condition of the patient. 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.

Your Key Worker

If you are diagnosed with CUP you will be 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.

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. If you decide to choose this option, you will be offered palliative care. This aims to control your symptoms and help you to keep your quality of life. You may be referred to the Community Palliative Care team for support when you leave hospital.

Your Key Worker names are Amanda Plewes, Emma Gollins and Kayleigh Bartle

Your Key Worker can be contacted on(01482) 461096 (answer machine available)

They are based at: Queens Centre, Castle Hill Hospital Castle Road, Cottingham, HU16 5JQ

Useful Information

Should you require further advice on the issues contained in this leaflet, please do not hesitate to contact your Key Worker on telephone numbers: (01482) 461096

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

We collect and use your information to provide you with care and treatment. As part of your care, information about you will be shared between members of a healthcare team, some of whom you may not meet. Your information may also be used to help train staff, to check the quality of our care, to manage and plan the health service, and to help with research. Wherever possible we use anonymous data.

We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.

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