Tests for cancer of unknown primary (CUP)
This page tells you about the tests you may have to find a cancer.
Tests for cancer of unknown primary (CUP)
If you have symptoms or feel unwell, you usually begin by seeing your GP. Some people first go to their doctor with a very general cancer symptom, such as a lump somewhere in the body or a swollen lymph gland. Your GP will examine you and ask about your general health. They will ask you about your symptoms and will probably want you to have some blood tests. If your doctor suspects that you may have cancer, they will refer you to a specialist at your local hospital.
At the hospital
At the hospital the specialist will examine you and ask you to have some tests. Scans may show that the lump is likely to be a cancer. Or your doctor may take a sample of cells (biopsy) from the lump or lymph gland. The biopsy result may show that the cancer is a secondary cancer – meaning that the cancer cells have spread from somewhere else in the body. At first it may not be obvious what type of cancer cells they are and this is called an unknown primary. Your doctor will ask you to have tests to try to find the primary cancer. The tests you may have include
- A biopsy, which means removing a sample of tissue and looking at it under the microscope – how the cells look may help your doctor to find out where the cancer started
Sometimes tests can't find the primary cancer so it continues to be called a cancer of unknown primary. If you have a very advanced cancer when you first go to the doctor, it may not be sensible to put you through endless tests just to find out the cancer type. If the cancer has spread widely around your body, it may make more sense to focus on keeping the cancer under control and treating your symptoms.
You can view and print the quick guides for all the pages in the Diagnosing CUP section.
If you have symptoms or feel ill, you usually begin by seeing your GP. Your GP will examine you and ask about your general health. They will ask you about your symptoms. This will include what the symptoms are, when you get them, and whether anything you do makes them better or worse. Your doctor will also ask you questions about your personal and family medical history.
Your doctor will examine you and may ask you to have some blood tests. Blood tests involve putting a needle into a vein in the arm and taking a small sample of blood. A blood test can give your doctor information about your general health. If your doctor suspects that you may have cancer, they will refer you to a specialist at your local hospital.
When you first go to see a specialist, they will ask you about your medical history and symptoms. The specialist will then examine you and probably do some more blood tests. These blood tests can give your doctor more information about your general health, whether you have low iron levels (anaemia) and how well your liver and kidneys are working.
Your doctor will want to carry out a number of other tests to try to find out what the problem is. These tests are useful for looking for different things in various parts of the body. Your doctor will choose between the tests, depending on the symptoms you have and the areas they want to check. The most common tests include
Your doctor may test your blood for chemicals that are produced by some common cancers. The National Institute for Health and Care Excellence (NICE) recommends certain tests according to the symptoms you have.
X-rays and CT scans use low level radiation (X-rays) to build up a picture of the inside of your body. There is detailed information about having a CT scan in the cancer tests section. You will almost certainly have an X-ray of your chest. In women, if the symptom that took you to the GP was a swollen lymph gland under your arm, your doctor will probably ask you to have a breast X-ray (mammogram).
If you have any bone pain, your doctor will ask you to have the painful bones X-rayed too. If the bone X-rays don't show up anything abnormal, your doctor may suggest you have a bone scan. There is information about having a bone scan in the cancer tests section.
Ultrasound scanners use sound waves. They are completely painless and have no side effects. They are helpful for finding lumps or abnormalities in the abdominal or pelvic areas. The only discomfort associated with them is that women may be asked to make sure they have a very full bladder when they have the scan. A full bladder helps to show up the womb and ovaries more clearly. There is information about having an ultrasound scan in the cancer tests section.
If you have a lump or a swollen lymph gland, your doctor may ask you to have a biopsy. This is the most important test for diagnosing unknown primary cancer. A biopsy means removing a sample of tissue and looking at it under the microscope. If the cells in the sample are very abnormal and don't look like the usual cells from that area of the body the doctor knows it is a secondary cancer.
If any of the tests above show that you have a secondary cancer your doctor will tell you. It can be very shocking to be told that you have a secondary cancer but that the primary cancer is not known. The hospital staff will do all they can to support you.
Your doctor may ask for further tests on the biopsy sample to try to find out where the primary cancer is. They may use tests such as immunohistochemistry tests which look for particular proteins on the surface of the cancer cells. These tests can sometimes tell which type of cell the cancer has grown from, for example, breast cells or lung cells.
Tests on the biopsy sample
Techniques called gene expression profiling and molecular profiling are now available for research purposes, but are not yet available on the NHS. Gene expression profiling aims to identify genetic patterns in cancer tissue. They look at the patterns of genes in the secondary tumour to try to find out the primary cancer. Molecular profiling looks at genetic material or particular molecules in the biopsy sample. These techniques can be used to find out the type of cancer cell. These tests are sometimes available in private hospitals.
Further scans or X-rays
You may also have further scans or X-rays. In some situations you may have an MRI scan, a PET scan or a PET-CT scan but this is not common. It is not yet clear how helpful these scans are in finding unknown primary cancer. There is information about research into these scans in the section about cancer of unknown primary research.
When you get the results
If your doctor can tell from your biopsy or your other tests where the cancer cells came from, you will no longer have a cancer of unknown primary. So, for example, if tests show that your cancer started in the stomach your cancer is a stomach cancer and will be treated as such, even if the primary tumour cannot actually be seen in the stomach.
Sometimes even after many tests the primary cancer cannot be found. If this happens your doctor will still be on the look out for signs or symptoms that could tell them what type of primary cancer you have. This could show up at any time, even after treatment when you are going for check ups.
If you have advanced cancer
If you have a very advanced cancer when you first go to the doctor, it may not be sensible to put you through lots of tests to find out the cancer type. If the cancer has spread widely around your body and is not likely to be a curable type, it may not help you to have more tests and scans. It may make more sense to focus on controlling the cancer for as long as possible and treating your symptoms, rather than having lots of tests to find out exactly which type it is.
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