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Diagnosing cancer in children

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on June 9, 2022.

Unlike with adults, there are no widely recommended screening tests to look for cancer in children who are not showing symptoms, and only a few are available for children known to be at an increased risk of cancer due to genes that have been passed down from their parents.

Certain symptoms, especially when they show up together, may raise the suspicion for cancer in children. These include:

  • Unusual lump or swelling
  • Unexplained paleness
  • Lack of energy
  • Easy bruising
  • Easy bleeding
  • Ongoing pain in one part of the body
  • Limping
  • Unexplained fever or illness that doesn’t go away
  • Frequent headaches
  • Vomiting
  • Sudden vision changes
  • Swollen or enlarged lymph nodes
  • Sudden and unexplained weight loss
  • Loss of appetite

These are fairly non-specific, and most of the time, these symptoms are caused by a condition other than cancer.

If your child’s doctor is concerned that a symptom or group of symptoms suggests a possible cancer diagnosis, certain tests and technologies may help determine what’s causing them. Your child’s doctor will likely refer you to a pediatric oncologist, a child cancer expert, to order the appropriate diagnostic tests and help you interpret the results.

Which combination of diagnostic tests and procedures your child’s doctor will order will likely be based on the symptoms he or she is experiencing.

Physical exam and blood and fluid tests

Physical exam Your child’s doctor will typically perform a thorough physical exam to identify unusual or concerning signs, such as swollen lymph nodes. This visit also involves a detailed discussion of exposure to potential cancer risks, such as radiation, and your family history of cancer. This important first step will help guide what comes next.

Complete blood count (CBC) and other blood tests A blood test may help begin to diagnose blood cancers and indicate other cancers. Blood is taken through a vein with a needle. A CBC blood test measures the number of red blood cells, white blood cells and platelets in the blood. A “differential” CBC also examines the different types of white blood cells to understand what may be going on in the body.
For instance, most children with leukemia will have too many white blood cells and not enough red blood cells and/or platelets. Many of the white blood cells in the blood of children with leukemia will be myeloblasts or blasts, an early type of blood cell that doesn’t function as well as mature white cells. Other blood tests, such as a peripheral blood smear, may produce information about the number and shape of different types of blood cells.

Tumor marker test —blood, urine, fluid, tissue biopsy Cancer cells may leave behind important evidence in tissue, blood, urine or other bodily fluids. These are called tumor markers. Your child’s doctor may request a sample of stool, blood, urine or other bodily fluid or tissue. This sample would be sent to the lab to look for tumor markers that may help determine the presence of cancer. There usually isn’t anything your child will need to do before one of these tests, with the exception of a biopsy. Your child may have to stop eating or drinking a few hours before a biopsy test.

Neurological tests

Neurological exam During a neurological exam, your child’s doctor will track your child’s reflexes, eye and mouth movements, ability to walk and other nervous system functions. The results of a neurological exam may suggest a brain or spinal cord tumor.

Biopsy and needle aspiration

Biopsy Biopsy involves removing some or all of a growth so that it can be examined closely under a microscope. This procedure is performed with either a needle or small incision. This is the definitive way to diagnose most types of cancer. There are many types of biopsies depending on the area of the body. A biopsy is most often performed as a day procedure without a hospital stay, but some patients may require a hospital stay.

Bone marrow aspiration and biopsy In performing a bone marrow aspiration, your child’s doctor would remove a sample of the fluid and cells from inside a bone with a needle. This is usually performed in the hip bone. Your child will lie on his or her side and may need local anesthesia to numb the area before the procedure. Liquid bone marrow aspirations help diagnose childhood leukemia and lymphoma. This test can be performed at the same time as a bone marrow biopsy, which retrieves a sample of the soft, spongy bone marrow tissue as well as fluid.

Lumbar puncture (spinal tap) During a lumbar puncture, your child’s doctor would use a needle to retrieve a sample of cerebrospinal fluid (CSF) that flows around the brain and the spinal cord to look for cancer cells or tumor markers. Your child will be given an anesthetic to numb the lower back before the procedure and possibly other medications to keep him or her calm during this test.

Imaging exams

With the variety of imaging exams and accompanying technology now available, doctors are able to better visualize and track cancer in children than ever before. The time involved depends on what body part needs to be imaged.

The hardest part may be getting your child to stay still during the test. Sometimes, sedatives are used if needed.

X-rays Your child’s doctor may order X-rays of an area of the body experiencing pain to evaluate for cancer-related bone destruction. Your child will need to lie still, but the procedure is painless.

CT scan Computed tomography (CT) scans create 3D views of your child's internal organs, bones, soft tissues and blood vessels to help diagnose and stage cancer. A special dye called a contrast medium may be injected in your child’s veins before a CT scan for a more detailed image. Lying still tends to be the hardest part of this test for children.

MRI Magnetic resonance imaging (MRI) creates pictures using magnetic fields. The doctor may suggest injecting a substance called gadolinium into your child’s vein to make any cancer cells appear brighter in the picture. The machine makes a loud thumping noise, and this may be hard for some children. While parents cannot be in the same room, a speaker will allow you to hear and talk with your child. MRIs can help doctors see brain and spinal cord tumors. Still, the type of tumor can only be determined by a biopsy.

Ultrasound An ultrasound uses sound waves to create a picture of the internal organs. Sound waves echo differently when bouncing off abnormal tissue, and this procedure may help your child’s doctor identify a potential tumor. A rounded device with a jelly ointment would be glided over the area of your child’s body being examined. This procedure is typically pain-free, but any soreness your child is having in the area may cause some mild pain.

PET-CT scan A positron emission tomography (PET) scan is combined with a CT scan to create pictures of organs and tissues inside the body. With this test, a small amount of a radioactive sugar (a tracer) is injected into your child’s veins. This sugar is taken up by cancer cells, which use more energy than healthy cells. A scanner can then detect this substance and produce images of inside of the body. This is a painless test except for a mild pinch when the tracer is injected. You may be given some instructions to follow to prepare for this exam if your child will be using a sedative to stay calm.

Bone scans Bone scans can check for bone cancer as well as infections in the bones and fractures. A very small amount of a radioactive material or tracer is injected into a vein. The tracer collects in the bones and can be detected by a scanner that passes over the body while the patient is lying still. This is also a painless test.

Supporting your child during diagnostic testing

Your care team will do what they can to make sure your child is physically and emotionally comfortable during testing. It’s important for you to be honest and age appropriate with your child, which will help him or her ask questions and feel safe over time. Practicing testing positions beforehand and walking through the test may also help all of you get prepared. Your cancer care team can help refer you to many resources to help you connect and communicate.

Your child’s doctor will review the results of tests with you as soon as they become available. Some, like biopsies, take time to come back. You may feel scared and anxious while waiting for results. Your child may be nervous, too. This is normal.

Try to remain upbeat and positive and also fit in the things you and your child need to do to stay healthy, such as eating well and getting regular physical activity. Try to also make time for the things you enjoy. Talking to a therapist or social worker may also help you and your child sort through this complicated time.

Show references
  • National Cancer Institute (2020, August 28). Childhood Cancers.
    https://www.cancer.gov/types/childhoodcancers#:~: text=In%20the%20United%20States%20in,to%20die%20from%20the%20disease.
  • National Cancer Institute. Children with Cancer A Guide for Parents.
    https://www.cancer.gov/publications/patient-education/children-withcancer. pdf.
  • American Academy of Pediatrics (2019, September 11). Look for red flags that raise index of suspicion for childhood cancer.
    https://www.aappublications.org/news/2019/09/11/focus091119.
  • American Cancer Society. (2019, February 12). Tests for Childhood Leukemia.
    https://www.cancer.org/cancer/leukemia-in-children/detectiondiagnosis- staging/how-diagnosed.html.
  • U.S. National Library of Medicine (2020, July 31). Tumor Marker Tests.
    https://medlineplus.gov/lab-tests/tumor-marker-tests/.
  • U.S. National Library of Medicine (2020, November). Helping your child understand a cancer diagnosis.
    https://medlineplus.gov/ency/patientinstructions/000844.htm.
  • Children’s Oncology Group. Tests and Procedures.
    https://childrensoncologygroup.org/index.php/testsandprocedures.
  • Radiological Society of North America (2019, February 20). Biopsies-Overview.
    https://www.radiologyinfo.org/en/info.cfm?pg=biopgen.
  • American Cancer Society (2018, June 20). Tests for Brain and Spinal Cord Tumors in Children.
    https://www.cancer.org/cancer/brain-spinalcord- tumors-children/detection-diagnosis-staging/how-diagnosed.html.
  • Radiological Society of North America (2019, January 30). Children's (Pediatric) CT (Computed Tomography).
    https://www.radiologyinfo.org/en/info.cfm?pg=pedia-ct#common-uses.