How Blood Cancers Are Diagnosed

If your doctor thinks you might have blood cancer, there are tests that can help them find out for sure. You may need to have more than one to know what’s going on.

Blood Tests

A nurse will take some blood from a vein in your arm, near your elbow. Your medical team can use the sample for:

Complete blood count: This common test measures the white blood cells, red blood cells, and other things that make up your blood. If the test finds too many or too few of some of them, that can be a sign of a problem.

Blood smear: If the complete blood count doesn’t give clear results or your doctor thinks your body isn’t making blood cells the way it should, they may recommend this test. It tells whether the blood cells look normal and if you’ve got the right amount of them.

Blood chemistry: This measures blood sugar, cholesterol, proteins, hormones, and other things in your blood. That tells your doctor about your overall health and can flag some problems. For example, certain proteins can show how big tumors are and how fast they’re growing.

White cell differential: This measures the different kinds of white cells in your blood. The results help show how well your body can fight infection. They also can show signs of some types of blood cancers, like leukemia, and tell how advanced they are.

FISH (fluorescence in situ hybridization): This focuses on blood cancer cells. It tells whether the genetic blueprint that guides their growth is changing. The results will help your doctor know if you’re getting the right treatment.

Flow cytometry: If your blood has too many white cells, this can tell if cancer is the reason for that. The test measures the number of white cells and notes their size, shape, and other traits. It can be done on your blood or your bone marrow.

Immunophenotyping: This can tell the difference between the types of cancer cells. That can help your doctor figure out the best treatment for you.

Karyotype test: This looks for changes in the size, shape, number, or arrangement of chromosomes in blood or bone marrow cells. It can help your doctor plan your treatment.

Polymerase chain reaction: This can spot markers of cancer. It can pick up on things that other tests miss and tell your doctor how well your treatment is working.


Bone Marrow Tests

Your bones are hard on the outside, but they’re more like sponge in the middle. That part is called the marrow, and it’s where your red blood cells and white blood cells are made.

Your doctor may need to find out if a disease is attacking your bone marrow. Some illnesses show up there before they do in your blood.

Your doctor probably will take a small amount of marrow from your hip. First, your medical team will numb the area. They also might give you medicine to make you drowsy.

Then your doctor probably will do two things:

  • Bone marrow aspiration: They'll use a hollow needle to take out a little of the fluid inside your bone marrow.
  • Bone marrow biopsy: They'll use a slightly larger needle to take out a piece of the solid part of the marrow.

It usually takes about 30 minutes. You might have it done in a hospital, clinic, or your doctor’s office.

The samples will go to a lab, where technicians will figure out whether your bone marrow is making enough healthy blood cells. They’ll also look for unusual cells. When the results get back to your doctor, they can help her:

  • Confirm or rule out certain illnesses
  • Figure out how advanced a disease is
  • See if treatment is working


Lymph Node Biopsy

Blood cancer may affect part of your immune system called your lymphatic system. The lymphatic system runs throughout your body, and it includes your tonsils and spleen, along with lymph nodes that are about the size of beans. Your body has hundreds of them, and they have white blood cells to help fight infections and illnesses.

Your medical team may want to take out part or all of a node to look for cancer. Doctors call that a lymph node biopsy.

The surgical team will take you into an operating room in either a hospital or an outpatient center. They’ll make the area numb around where they’re going to take out the node, but they probably won’t put you to sleep.

Your doctor will make a small cut and take out the node, then close the spot with stitches. It shouldn’t leave a scar.

When your medical team studies the lymph node, they can look for cancer tumors, masses that aren’t cancerous, or infections. That can tell them whether you have lymphoma, a kind of cancer that attacks the lymphatic system.


Imaging Tests

These painless tests let your doctor see inside you. They may show tumors or other conditions.

Chest X-rays: These can help your doctor spot a tumor, an infection, or a large lymph node.

CT (computed tomography) scan: Your doctor will use a machine that takes X-rays from different angles and put them together to make a more complete picture. That can show large lymph nodes, and other organ abnormalities, or help your doctor see if cancer has returned after treatment. To get the test, you lie on an exam table, and the scanner rotates around you. It usually takes 10 to 30 minutes.

MRI (magnetic resonance imaging) scan: This uses a powerful magnet and radio waves to make detailed pictures of your organs, blood vessels, or bones. It can help your doctor spot tumors or look for changes in your bones that signal a type of blood cancer called myeloma. You’ll lie on a table that slides you inside a machine that’s like a little tunnel. If going into a tight space makes you anxious, the medical team may give you medicine to relax you. The exam takes 15 to 45 minutes.

PET (positron emission tomography) scan: This uses a radioactive form of sugar to show your metabolism at work. It can tell your doctor if you have lymphoma or other cancers. When you get the test, the technician will give you a shot that has the sugar in it. You’ll lie down on an exam table, and it will slide you inside the scanner. If small spaces stress you out, the team may give you medicine to relax you. It takes around 45 minutes.

Spinal Tap

This test looks at a sample of the fluid around your brain and spinal cord. It can tell your doctor if the fluid has any blood cancer cells. You may hear this test called a lumbar puncture.

You’ll lie on your side, and your medical team will make part of your back numb. Then your doctor will use a needle to take out a little fluid from between the bones in your spine. They'll put a bandage on the spot in your back, and the fluid sample will go to the lab.


Urine Test

This measures proteins, blood cells, and other substances in your urine. Chemicals in your blood often end up in your urine after your kidneys filter them out.

WebMD Medical Reference Reviewed by Jennifer Robinson, MD on June 12, 2020



Leukemia & Lymphoma Society: “Lab and Imaging Tests,” “Blood Tests,” “Bone Marrow Tests,” “Lymph node biopsy,” “Imaging tests,” “Lumbar puncture,” “Urine test.”

NCI Dictionary of Cancer Terms: “Bone marrow,” “Lymph node.”

Mayo Clinic: “Bone marrow biopsy and aspiration,” “Parts of the immune system.”

American Society of Hematology: “Blood Cancers.”

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