On this page: What is cancer of unknown primary? | Why can't the cancer be found? | Does it matter it can't be found? | Will I need lots of tests? | What are the different cell types? | What are the causes? | What are the symptoms? | How common is CUP? | Key points
This is a cancer that has spread from somewhere else in the body, but it’s not clear where in the body it started.
For most people who have cancer, the primary cancer is easy to identify. Doctors conduct tests to find where in the body the cancer started to grow. They may also do other tests to see if the cancer has spread.
When cancer is found in one or more secondary sites but it is not clear from the test results where the cancer began, the cancer may be called cancer of unknown primary or CUP.
There are several reasons why the primary cancer cannot be found. It may be that:
Finding the primary cancer helps doctors decide what treatment to recommend. If it can’t be found, the treatment path can be less clear. However, doctors try to learn as much as they can about the spread of the cancer, the cells involved, your symptoms and medical history to help plan treatment.
Many people find they need several tests to try to find where the cancer started. The tests may take time and be tiring, particularly if you are feeling unwell. You may also feel frustrated if the tests don’t find the site of the primary cancer.
You may want to talk to your doctor about the number of tests needed. They will only suggest tests they feel are necessary. Ask your doctor or nurse to explain the tests and how they’ll impact on your care, as this information can help you make an informed decision about having the tests.
At some point your doctors may decide that having more tests won’t help find the primary site. It may be of more benefit to you to focus on controlling the symptoms.
Even if you decide against having further tests, you may find your family and friends encourage you to continue. This can be a challenging situation and it may help to explain your decision to your loved ones.
Even if tests can’t find where the cancer started, your doctor will try to discover the type of cell the cancer developed from. Knowing the type of cell may give doctors a clue as to where the cancer started.
Cancer is a group of more than 200 different diseases. Each type of cancer has different risk factors, such as getting older, poor diet, smoking, excessive alcohol consumption, being obese and certain infections. These may play a role in CUP.
Symptoms are different for everyone and are related to the area where the secondary cancer is found. Some people with CUP have few or no symptoms; others have a range of symptoms that may include:
You may also have general symptoms such as unexplained weight loss, no appetite or feeling extremely tired.
CUP is more common than many people realise.
It is the eighth most common cancer in Australia. It is the seventh most common cancer in women and the ninth most common in men. There are nearly 3000 new cases of CUP diagnosed each year in Australia.
Reviewed by: A/Prof Linda Mileshkin, Consultant Medical Oncologist, Division of Cancer Medicine, Peter MacCallum Cancer Centre, VIC; Karen Hall, Nurse Counsellor, Helpline, Cancer Council SA and Clinical Nurse, Oncology/Haematology Inpatient Unit, Flinders Medical Centre, SA; A/Prof Chris Karapetis, Director of Clinical Research, Medical Oncologist, Flinders Centre for Innovation in Cancer, SA; A/Prof Claire Vajdic, Team Leader, Cancer Aetiology and Prevention Group, Prince of Wales Clinical School, Lowy Cancer Research Centre, University of NSW, NSW; and Robyn Wagner, Consumer.