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Cancer of Unknown Primary: Tests After Diagnosis

What tests might I have after being diagnosed?

After a diagnosis of cancer of unknown primary (CUP), you will likely have other tests. Doctors will repeat a careful physical exam and maybe some of the tests you had as part of diagnosing the CUP. They will have a second pathologist look at the biopsy samples.

This help your health care providers learn more about your cancer. The tests can help show if and where the cancer has spread throughout the body. They can also help your doctors find out where the cancer first started. The test results help your healthcare providers decide the best ways to treat the cancer. If you have any questions about these or other tests, be sure to talk with your healthcare team.

Sometimes, as time passes, a small, hidden primary tumor may grow large enough to be found. This may help the healthcare providers figure out what’s causing the CUP.

The tests you have will depend on where the cancer is found. The tests you have can include:

  • Blood and urine tests

  • Imaging tests

  • Procedures called biopsies

Blood and urine tests

Blood cell count

Your healthcare provider may check the numbers of certain blood cells. Changes in blood cell counts may mean that cancer has spread to your bones and bone marrow cells.

Liver and kidney function

If either of these tests is abnormal, this may mean that these organs are the primary site of the cancer.

Tumor marker tests

Some kinds of cancer release proteins or special markers into your blood or urine. If certain markers are found in your blood, your healthcare providers may be able to tell what kind of cancer you have. For instance, a man may have high prostate-specific antigen (PSA) levels in his blood. This might mean that the cancer may have started in his prostate gland.

Imaging tests

Imaging tests show what’s happening on the inside of your body. You may have one or more of these imaging tests. This depends on where the CUP is found.


This test uses sound waves to look for problems in your internal organs. Like sonar on a submarine, the machine sends out sound waves that bounce off body parts. Then it sends back an image. A computer then uses the signals to create an image of your body. Ultrasound images can help your healthcare provider spot growths.

Computed tomography or CT scan

In this test, an X-ray beam moves around your body while a machine takes pictures from many angles. These pictures are combined by a computer. This gives your healthcare provider detailed cross-section images of your body.

Magnetic resonance image (MRI)

An MRI uses magnets and radio waves to take pictures of the inside of your body. In many cases, MRIs can show more details about your internal organs than other imaging tests.

Positron-emission tomography or PET

Cancer cells use sugar (glucose) differently than normal cells. This test uses a radioactive sugar solution to make images. These images show how the different cells in your body use glucose for fuel. Then, a special type of scanner takes pictures to see which cells are using the most glucose.  Cancer cells tend to need more glucose than normal cells.

Bone scan

This is a test where a radioactive dye is injected into your veins. The dye will travel to and be taken up by your bones. Cancerous growths in bone take up the dye differently than normal bone.


For this test, your healthcare provider uses a long, narrow tube with a light and a camera on the end. This tube may be put into a natural body opening. It may be put in your mouth to look at your stomach or breathing tubes and lungs. Or it may be placed in your anus to look at your rectum and colon. Whether this test is used and where it may be used depends on where the CUP is found.


If cancer is found in the lymph nodes in your armpit, you may need a mammogram. This test looks for tumors in your breast.


You may have a test called a biopsy. During a biopsy, your healthcare provider takes tissue samples from areas that might be cancer, such as swollen lymph nodes. A doctor who checks tissues (pathologist) then looks at the samples under a microscope. There are many types of biopsies that can help find out where the cancer started.

Fine needle aspiration

In this test, your healthcare provider uses a very thin needle to remove some fluid or a small amount of tissue from the tumor.

Core needle biopsy

Your healthcare provider can take out more tissue in this test. The needle is wider than the one used in a fine needle aspiration.

Paracentesis or thoracentesis

For paracentesis, your healthcare provider uses a needle to remove fluid from your abdomen. For thoracentesis, your healthcare provider uses a needle to remove fluid from the area around your lungs. The pathologist can tell if the fluid contains cancer cells.

Bone marrow aspiration or biopsy

Your healthcare provider will remove a small amount of bone marrow fluid and a piece of bone tissue. He or she uses a special needle to take these samples. This is usually done from the back of your hip bone.

Excisional biopsy

A surgeon removes the entire tumor in one piece. He or she may also remove lymph nodes that could contain cancer. Then a pathologist checks the tissue for signs of cancer.

Incisional biopsy

A surgeon takes out only a part of the tumor. This method is used if the tumor is so large that taking out the whole tumor may cause complications. A pathologist checks the tissue for signs of cancer.

Diagnostic pathology tests

The pathologist uses a range of tests to help find signs of cancer. This can also help find the source. The pathologist stains the tissue samples to find tumors. These can include sarcomas, melanomas, and lymphomas.

Other special stains help spot tumors or cells that may have come from the testicle, prostate, breast, thyroid gland, or colon. The pathologist may also view the sample under an electron microscope. This special microscope can show more details that give clues about the origin of the cells.

Finally, your healthcare provider may do specialized molecular tests. These tests look for any genes that may have problems. Different damaged genes may lead to different kinds of tumors.

Working with your healthcare provider

Your healthcare provider will talk with you about which tests you'll have. He or she will tell you how to get ready for these tests. Make sure you follow your healthcare provider’s orders. Ask him or her questions and talk about any concerns you have.

Online Medical Reviewer: Gersten, Todd, MD
Online Medical Reviewer: Stump-Sutliff, Kim, RN, MSN, AOCNS
Date Last Reviewed: 5/1/2016
© 2013 The StayWell Company, LLC. 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.
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