Cancer of unknown primary


Diagnosis

Page last updated: October 2024

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Before CUP is diagnosed, you will usually see your GP, who will ask about your symptoms and medical history, examine you, send you for tests and refer you to a specialist doctor.

The specialist will arrange extra tests to work out whether you have primary or secondary cancer. If the tests show that the cancer is secondary, more tests will be done to try to find the primary cancer. The tests you have depend on your health and symptoms, the location of the secondary cancer and the suspected location of the primary cancer.

The diagnosis and treatment of CUP can be complex and you might need to travel to a specialist centre. Call Cancer Council 13 11 20 to ask about patient travel assistance that may be available to you.

Your guide to best cancer care

A lot can happen in a hurry when you’re diagnosed with cancer. The guide to best cancer care for liver cancer can help you make sense of what should happen.

It will help you with what questions to ask your health professionals to make sure you receive the best care at every step.

Read the guide

 

Tests used to find where the cancer started

  • Blood and urine tests – samples of your blood and urine are sent to a laboratory to be checked for abnormal cells and chemicals called tumour markers
  • Biopsy – a tissue sample is taken from a tumour, enlarged lymph node or bone marrow and sent to a laboratory for examination; tests on the sample can suggest the primary site 
  • Endoscopy – uses an instrument to look inside the body and take small tissue samples
  • Imaging tests – x-rays, ultrasounds and other scans create images of the inside of the body; PET–CT scans have been shown to help find the primary site in new cases of CUP

If the tests find where the cancer started, the cancer is no longer an unknown primary. It will then be treated like the primary cancer type. For example, bowel cancer that has spread to the liver will be given the treatment for advanced bowel cancer.

Blood and urine tests

A full blood count is a test that checks the levels of red blood cells, white blood cells and platelets. Blood tests can also show how well the kidneys and liver are working. Urine and faeces (poo) may be tested to look for abnormal cells or bleeding coming from the bladder, kidneys or bowel.

Tumour markers

In some cases, blood, urine or tissue samples may be tested for tumour markers. These are proteins made by some cancer cells. High levels of tumour markers may suggest cancer.

However, other conditions can also raise the levels of tumour markers, and some people with cancer have normal levels. Tumour marker levels can’t be used on their own to diagnose the primary cancer, but they may suggest certain types of cancer for your doctors to look for.

Biopsy

A biopsy is when doctors remove a sample of cells or tissue from an area of the body. A specialist doctor called a pathologist examines the sample under a microscope to look for signs of cancer and work out what type of cell is affected. This can point to where in the body the cancer may have started.

For a biopsy, you will usually have a local anaesthetic to numb the area. In some cases, you may need a general anaesthetic, which puts you to sleep.

Ways of taking biopsies

Looking at the molecular level

Endoscopy

This procedure is used to look inside the body for any abnormal areas. It is done with an endoscope – a thin, flexible tube with a light and camera on the end. The endoscope is put into the body through a natural opening (such as the mouth) or a small cut made by the surgeon.

The camera projects images onto a monitor so the doctor can see inside the body. If they see something suspicious, they can also take a tissue sample (biopsy) using the endoscope.

Common types of endoscopy

Type of endoscopy
 Part of the body tested Where the tube is inserted
bronchoscopy or endobronchial ultrasound (EBUS) lungs or respiratory tract (airways)  mouth or nose
colonoscopy colon (large bowel)  anus
colposcopy vagina and cervix placed outside the vulva and vagina, held open by a speculum
cystoscopy bladder  urethra
gastroscopy oesophagus, stomach and first part of the small bowel  mouth
hysteroscopy uterus (womb)  vagina
laparoscopy abdominal cavity, liver, bowel, uterus and ovaries  small cuts in the abdomen
laryngoscopy larynx (voice box)  mouth
sigmoidoscopy lower part of the colon (large bowel)  anus
thoracoscopy lungs  small cut in the chest

 

Imaging tests

These scans create images of the inside of your body and provide different types of information. Your doctors will recommend the most useful scans for your situation. Ask your doctor or imaging centre what you will have to pay and whether Medicare covers the cost.

Before having scans, tell the doctor if you have any allergies or have had a reaction to dyes during previous scans. You should also let them know if you have diabetes or kidney disease, or are pregnant or breastfeeding.

X-ray

Ultrasound

CT scan

PET-CT scan

Bone scan

MRI scan

 

Staging is a way to describe the spread of cancer. However, CUP cannot be given a stage because the primary cancer is not known and the cancer has already spread to other parts of the body when it is found.

This is considered advanced cancer. For more information, read Living with Advanced Cancer and listen to our podcast series, The Thing About Advanced Cancer.

Gary's story

"At the time of my diagnosis, I was working as a senior lawyer. One morning, I was on the phone to a client and looking out the window. I was running a hand over my chin when I felt a lump. I actually said to the client, 'I've just felt this lump, so I'm going to see my GP. Goodbye.'

"I had to have a needle biopsy the next day and the results of that were significant. It was squamous cell carcinoma and it was metastatic.

"The doctors did another couple of biopsies to look for the primary, but they couldn't find it. They guessed the cancer had started in my mouth, but I had a fair complexion and red hair, so it might also have started somewhere on my skin.

"I had surgery to take out most of my molars, then more surgery to remove all the lymph nodes down one side of my neck.

"Even though we hadn't found the primary cancer, I talked about the treatment options with my doctors and we agreed to forge ahead. I was 51 and fit, so we decided on a broad approach with a combination of strong chemotherapy and radiation therapy.

"The cancer diagnosis knocked me for six. I went into a deep black hole. The fact that it was CUP didn't affect me at the time – I actually didn't grasp what metastatic meant.

"I like to think that I'm a fairly optimistic and together person, but after the treatment was over, I struggled with anxiety about the cancer recurring. The fact that the primary cancer wasn't found added to that anxiety – it was an extra element.

"I ended up seeing a psychiatrist about a year after my treatment, but it would have been better to get that sort of help earlier."

Prognosis

Prognosis means the expected outcome of a disease. You may wish to discuss your prognosis and treatment options with your doctor, but it is not possible for anyone to predict the exact course of the disease.

To work out your prognosis, your doctor will consider test results; the type of CUP you have; where the cancer is located and how far it has spread through the body; how fast the cancer is growing; how well you respond to treatment; the impact the cancer has had on your health; and factors such as your age, fitness and medical history.

Although most cases of CUP can’t be cured, treatment can keep some cancers under control for months or years. Whatever the prognosis, palliative treatment can relieve symptoms such as pain to improve quality of life. It can be used at any stage of advanced cancer.

Discussing your prognosis and thinking about the future can be challenging and stressful. It is important to know that although the statistics for CUP can be frightening, they are an average and may not apply to your situation. Talk to your doctor about how to interpret any statistics that you come across

Get support

Many people feel shocked and upset when told they have cancer. It can be even more distressing if the cancer has spread and the original (primary) site cannot be found.

Cancer Council's experienced nurses can help you connect with other people who are living with advanced cancer, and provide you with information about the emotional and practical aspects of living with CUP.

Contact cancer support

Understanding Cancer of Unknown Primary

Download our Understanding Cancer of Unknown Primary booklet to learn more and find support.

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