Cancer of unknown primary assessment

What is a cancer of unknown primary assessment?

Sometimes a cancer is found only after it has already spread, and it is not clear where in the body it started. The place a cancer begins is called the primary; the spread is called secondary or metastatic cancer. When the secondary cancer is found but the primary is not obvious, this is called cancer of unknown primary, or CUP. A cancer of unknown primary assessment is the careful set of tests and specialist reviews used to try to find the source and to plan the best treatment.

The assessment usually includes examining a sample of the cancer under a microscope, special staining of that sample (immunohistochemistry) to look for clues about its origin, blood tests, and scans such as CT and sometimes a whole-body PET-CT. Doctors use the pattern of where the cancer is, what it looks like and how it behaves to work out the most likely starting point.

In the UK, this is coordinated by a dedicated CUP team (usually an oncologist, a specialist nurse and a palliative care doctor), so that one team holds the picture together and you have a clear point of contact. About 1 in 25 cancers (around 4%) cannot be traced to a clear primary site even after thorough tests.

This guide explains the assessment honestly. It cannot promise that the source will be found, and finding the source is not the same as being cured. It does not replace the discussions you should have with your own CUP team.

Types, options & approaches

There may be different ways to do this. The right approach depends on the clinical question and your circumstances.

Stages of a CUP assessment (NICE terms)

Not everyone goes through every stage. If you are very unwell, the team may sensibly limit testing to what will actually change your care.

Preparing for your test

• Ask which CUP team is coordinating your assessment and who your named contact (key worker) is.
• Bring any previous scans, biopsy results or hospital letters, as earlier results can hold important clues.
• Bring a full list of your medicines and your medical history, including any past cancers, which can be relevant.
• Ask which tests are planned, what each one is for, and whether a biopsy is needed.
• Ask whether you are well enough for extensive testing, and which tests will actually change your treatment.
• Plan practical support and transport, as several appointments may be needed over days to weeks.
• Write down your questions and consider bringing someone with you, as a lot of information comes quickly.

What happens

The assessment is a sequence of steps rather than a single test. First, a sample of the cancer (from a biopsy or fluid) is examined under a microscope and stained to look for clues about its origin, and you have blood tests and scans such as CT. The CUP team reviews these results together.

Depending on what the early tests show, you may have further, targeted investigations — for example a whole-body PET-CT, an endoscopy, a mammogram, or molecular tests on the cancer — chosen because they could change your treatment. The team decides which tests are worthwhile, balancing the chance of finding the source against how well you are and whether the result would alter the plan.

If the source is found, your care moves to the pathway for that cancer. If the source is not found despite thorough testing, this is called confirmed CUP, and the team plans treatment based on the most likely origin and on how the cancer is behaving. Throughout, a specialist nurse is usually your main point of contact, and the assessment runs alongside support for any symptoms.

Is this test right for me?

A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.

Before you decide

Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.

Comfort, sedation or contrast choices

If local anaesthetic, sedation, contrast or pain relief is used, ask what is planned, why, and what it means afterwards.

The biggest difficulty with a CUP assessment is uncertainty: even careful testing does not always find where the cancer started, and the search has to be balanced against how well you are. More tests are not always better — what matters is whether a test would change your treatment. Ask your team clearly: which tests will actually change my care, am I well enough for them, and what is the plan if the source is never found.

Published figures to discuss

CUP is, by its nature, uncertain. Whether the source is found, and the outlook, depend on the type of cancer, where it has spread and how it responds to treatment. The figures below are cautious population averages from Cancer Research UK and reflect that CUP is often advanced when found; there are no UK-wide survival statistics for CUP, and these figures cannot predict any individual's outcome. Use them only to understand the uncertainty, and discuss your own situation with your team.

These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.

What happens afterwards

There is usually no physical recovery from the assessment itself, apart from the minor after-effects of a biopsy. The harder part is often the wait for results and living with uncertainty while the picture comes together. Once the assessment is complete, your team explains what was found and what it means for treatment.

• Feeling anxious or unsettled while waiting for results
• Mild soreness or bruising for a few days after a biopsy
• Needing more than one test, or a repeat biopsy, to get a clear answer
• A period of uncertainty before a treatment plan is agreed
• Relief, or sometimes frustration, depending on whether the source is found

Aftercare

• Make sure you know who your named contact (key worker) is and how to reach them.
• Look after any biopsy site as advised and report signs of bleeding or infection.
• Keep a written record of the tests done, the results so far, and the planned next steps.
• Ask for clear explanations of what each result means and what is still uncertain.
• Tell your team about any new or worsening symptoms, as these can guide the search.
• Accept emotional support — uncertainty in CUP is hard, and specialist nurses and charities can help.
• Attend the follow-up appointments where results are explained and the plan is agreed.

• The name and number of your CUP key worker or specialist nurse
• A clear list of which tests are planned and what each is for
• Any previous scans, biopsy results and letters gathered together
• Biopsy-site care instructions and what to watch for
• A note of your medicines and full medical history, including past cancers
• Transport and support arranged for several appointments
• Someone to come with you when results are explained

⚠ Get urgent help if…

• Heavy bleeding, increasing pain, swelling or discharge at a biopsy site
• A high temperature, shivering or feeling very unwell after a biopsy (possible infection)
• Breathlessness, chest pain or coughing up blood (especially after a chest or lung biopsy)
• Severe tummy pain, dizziness or feeling faint after a biopsy of an internal organ
• A rash, swelling or difficulty breathing after contrast dye (possible reaction)
• Any rapidly worsening symptom, such as severe pain, confusion or collapse
• Any symptom your team has told you to report urgently

Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.

General guidance — it doesn't replace the specific advice your specialist gives you.

Results & realistic expectations

A good outcome from the assessment is a clear answer about where the cancer started, which usually allows more specific treatment. Often the tests narrow the likely source enough to plan sensible treatment even without complete certainty. Sometimes, despite thorough testing, the primary is never confirmed; this is honestly called confirmed CUP, and treatment is then based on the most likely origin and how the cancer is behaving.

It is important to understand that finding the source is not the same as being cured, and that the assessment is about getting the best information to guide care, not a guarantee of outcome. Your team can explain what your particular results mean, including what remains uncertain.

The results of the assessment guide treatment, but the picture can change over time: occasionally a primary site becomes clear later, new symptoms point to a source, or repeat tests are needed. Treatment plans in CUP are therefore reviewed as things develop. Outlook depends heavily on the type of cancer, how far it has spread and how it responds to treatment, and there are no UK-wide survival figures for CUP, so your team will talk about your own situation rather than a single number.

Related tests, treatments or support

A CUP assessment usually runs alongside care for any symptoms the cancer is causing, such as pain or breathlessness, and alongside discussions about treatment options. Once the most likely origin is identified, the assessment connects to the relevant cancer pathway, and supportive or palliative care can be involved at any stage.

Follow-up & long-term care

After the assessment, the CUP team explains the findings and either moves your care to the pathway for the identified cancer or agrees a treatment plan based on the most likely origin. You should have a named contact, a clear plan for any further tests, and a route to report new symptoms quickly. If the picture changes, the plan is reviewed, and support for symptoms and wellbeing continues throughout.

Repeat, follow-on and what comes next

• An initial biopsy is sometimes not enough and needs repeating, or further special staining, to get an answer.
• Tests may be done in stages, with each step deciding whether the next is worthwhile.
• A primary site occasionally becomes clear later, after the initial assessment, and the plan is then revised.
• If a result is inconclusive, the team may treat based on the most likely origin rather than keep searching.

Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.

What good aftercare looks like

• A named CUP key worker or specialist nurse as your single point of contact
• A clear explanation of what was found, what is still uncertain, and the plan based on the most likely origin
• Tests chosen because they could change your care, not testing for its own sake
• Prompt symptom and palliative support running alongside the assessment
• Coordination with your NHS team and GP, and a route to review the plan if new clues appear

What affects the cost

Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:

• How many and which tests are needed (biopsy, scans, special staining, molecular tests)
• Whether a whole-body PET-CT or MRI is used as well as CT
• Specialist pathology, including immunohistochemistry and any gene testing
• The CUP team review and specialist nurse support
• Any procedures to obtain a sample, and any inpatient stay if you are unwell
• Follow-up appointments where results are explained and a plan agreed
• Whether care is coordinated with the NHS, which funds most cancer assessment

• Exactly which tests are included, and what each one is for
• Consultant and CUP team fees and any facility or biopsy procedure fees
• Specialist pathology, immunohistochemistry and any molecular or gene testing
• Scans, including any PET-CT or MRI, and contrast if used
• Specialist nurse access and follow-up appointments to explain results
• What happens if a biopsy sample is inadequate and needs repeating
• What happens, and who pays, if a complication occurs or further tests are needed

On the NHS? Almost all of this assessment is provided and funded by the NHS through a dedicated CUP team; private care is generally used for speed of testing or a second opinion rather than for a different chance of finding the source or a cure.

You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.

Consent traps and marketing red flags

These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.

Choosing a specialist safely

• Check the specialist is on the GMC Specialist Register for this area.
• Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
• You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
• Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
• You're entitled to your total cost in writing — including any follow-up — before you decide.

How Vuemedics verifies every consultant →

Take this to your consultation. A good specialist will welcome every one of these.

• Which CUP team is coordinating my care, and who is my named contact?
• Which tests are you planning, what is each one for, and am I well enough for them?
• Which results would actually change my treatment?
• If the primary site is found, what does that mean for my treatment?
• If the source is never confirmed, how will you decide my treatment, and based on which clues?
• What support is there for symptoms and for the uncertainty while we wait for answers?
• When and how will all the results be explained to me, and who should I contact with new symptoms?
• Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
• Will you be the specialist who carries out my test, and who looks after me afterwards?
• What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
• What does a realistic result look like — and what can this test not achieve?
• What are my options, including waiting, doing nothing for now, or choosing a different approach?
• Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
• What is the total cost in writing, including any follow-ups, and how much time do I have to decide?

Find a verified specialist for cancer of unknown primary assessment

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How we made this page

Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →

Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.

Sources & standards: NICE — Metastatic malignant disease of unknown primary origin (CG104) Cancer Research UK — Tests for cancer of unknown primary (CUP) Cancer Research UK — CUP survival

Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.

Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.