Biopsy for cancer of unknown primary (CUP)

A biopsy means taking a sample of tissue so that it can be looked at under a microscope. This is the only way to be certain if an abnormal area is cancer or not.

Your doctor takes a sample of the abnormal tissue and sends the sample to the lab. This is where a doctor called a pathologist looks at it under a microscope and checks for abnormal or cancerous cells.

There are different ways to have a biopsy. 

How you have a biopsy

You might have a biopsy under general anaesthetic, which means you are asleep during the procedure.

Or you might have it under local anaesthetic, which numbs the area before the doctor takes the sample of tissue. Sometimes you may have a drug to make you drowsy (sedation) if you’re having a local anaesthetic.

Doctors use x-rays and scans, such as ultrasound or CT scan, to help guide many types of biopsy.

Types of biopsy

There are different types of biopsy. The type you have depends on where in the body the abnormal area is.

A needle biopsy takes a small sample of tissue from an abnormal area. There are 2 types of needle biopsy:

  • fine needle aspiration (FNA)
  • core biopsy

You usually have a needle biopsy under local anaesthetic.

Fine needle aspiration

Your doctor uses a thin needle to go through the skin and into the abnormal area. They take out a sample of tissue through the needle and into a syringe.

Your doctor can feel where to put the needle in if the abnormal area is near the surface of your skin. For areas deeper in your body they’ll use a scan to help guide the needle.

The tissue sample is then sent to the lab where a pathologist looks at it under a microscope.

Core biopsy

This is similar to having a fine needle aspiration, but the doctor uses a thicker needle. This means they can remove a larger sample of tissue. A core biopsy can be more useful as it allows doctors to do more tests on the tissue sample. 

Your doctor takes a sample of tissue by making one or more small cuts through the skin. They may remove the whole abnormal area if it isn’t too large. For example, they may remove a swollen (enlarged) lymph node. This is called an excisional biopsy.

Or you may have just part of the abnormal area removed (incision biopsy). This can happen when the abnormal area is too large or too complicated to remove (for example, it might be near an important part of your body).

You have a surgical biopsy under local anaesthetic or general anaesthetic.

An endoscopy is a test that looks inside the body, for example in your stomach or bowel. The endoscope is a long flexible tube that has a tiny camera and light on the end of it. Your doctor can see the images on a TV screen.

Diagram of an endoscopy

There are different types of endoscopy depending on which part of the body is being looked at. For example:

  • colonoscopy – to look at the inside of your large bowel (colon)
  • cystoscopy – to look at the inside of your bladder
  • bronchoscopy – to look inside your windpipe (trachea) and lungs
  • Endoscopic retrograde cholangio pancreatography (ERCP) – to look at your liver, pancreas and bile ducts

Your doctor might attach an ultrasound probe to the endoscope. This is called an endoscopic ultrasound. Ultrasound uses sound waves to build up a picture of the area. Your doctor might use it to look at your food pipe (oesophagus), stomach and the area around it. They may be able to see if nearby lymph nodes are swollen (enlarged).

During the test, doctors can put small surgical instruments through the endoscope to take samples of tissue.

In some cases, your doctor may want to take samples of your bone marrow. Bone marrow is the spongy tissue that is inside your bones. It makes your blood cells.

During the test, your doctor uses a needle to remove a sample of liquid bone marrow. They may then use a second needle to take out a piece of more solid bone marrow tissue. This is usually from the back of your hip bone. 

Diagram showing a bone marrow test

Cancer can sometimes cause fluid to collect around the lungs (pleural effusion) or tummy (ascites).

Doctors can use a need to take a sample of fluid to check for cancer cells. You usually have this done under local anaesthetic.

After the test

Your doctor sends the tissue samples to the lab, where a pathologist looks at the cells under the microscope.

You may go home the same day or the next day. This will depend on the type of biopsy you had.

Having a biopsy can be uncomfortable and your doctor may give you painkillers. The team will tell you if you need to follow any instructions when you get home, such as how to care for the wound if you have one. They will also tell you who to contact if you have any problems after your biopsy.

Getting your results

You usually get the results within 2 weeks. The doctor who arranged the biopsy will give them to you.

Waiting for test results can be worrying. It may help to talk to a close friend or relative about how you feel.

For support and information, you can call the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday.
Last reviewed: 
16 Jun 2021
Next review due: 
16 Jun 2024
  • Cancer and its Management (7th edition)
    J Tobias and D Hochhauser
    Wiley-Blackwell, 2015

  • Metastatic malignant disease of unknown primary origin in adults: diagnosis and management
    The National Institute for Health and Care Excellence (NICE), 2010

  • The Royal Marsden Manual of Clinical Nursing Procedures, 10th Edition
    S Lister and others (Editors)
    Wiley-Blackwell, 2020

  • Cancers of unknown primary site: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow up

    K Fizazi and others

    Annals of Oncology, 2015. Vol 26, supplement 5

  • Pleural effusion
    BMJ Best Practice, last accessed May 2021

  • Assessment of ascites
    BMJ Best Practice, last accessed May 2021

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