How is cancer of unknown primary diagnosed?


If you have symptoms, a doctor may use several tests to see if you have cancer that has metastasised (spread). Your doctor will try to find the primary cancer. If they can’t find it, the doctor will try to find the type of cell that the cancer started from. 

Physical examination and medical history

A doctor will check your body to look for lumps and other signs of cancer. They will also ask you about your medical history. 

Blood tests

A blood test can tell your doctor about the number and types of blood cells you have, and measure levels of other signs of cancer (called tumour markers). 

Urine or stool analyses

A urine analysis can tell the doctor about your overall health, including problems with your kidneys or bladder.  

Doctors can also look for microscopic levels of blood in your stools. 


For some types of tumours, you may have an endoscopy. This uses a thin tube (called an endoscope) with a light and camera on it to look at the inside of your body. Some endoscopes can also use ultrasound to get a more detailed picture (called an endoscopic ultrasound or EUS). Your doctor may also be able to take a biopsy (small tissue sample) using an endoscope. This will be sent to a laboratory for analysis. 

There are different types of endoscopies, depending on the body part being examined. Examples are: 

  • colonoscopy, to look inside the colon 
  • gastroscopy, to look at the stomach and first part of the bowel 
  • laparoscopy, to look at the internal abdominal organs such as stomach, liver and female reproductive organs. 

Imaging tests

Depending on your symptoms, you may have X-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI), ultrasound, positron emission tomography (PET) scans or bone scans.  


A biopsy is when the doctor takes a sample of tissue of the tumour or abnormal area through a needle. This sample is then sent to look at under a microscope and do laboratory tests for signs of abnormal cells.