Childhood cancer is rare, and more readily diagnosed and treated than ever. With better testing to tell between the specific types of cancers and better cancer treatments available, more than 80% of children and adolescents with cancer will survive.
Signs and symptoms of cancer often mimic other illnesses. Pediatricians concerned about a possible cancer will refer your child to a pediatric oncologist, a doctor who specializes in diagnosing and treating childhood cancers. The specialist will need to get a thorough medical, social, and family history, as well as a physical examination. They may also order different tests to determine the different types of cancers.
What are some common tests used to diagnose cancer?
Below are some of the more common tests used to diagnose cancer in children and teens. Not all of the tests mentioned here are necessary to diagnose every cancer.
Blood tests help look for cancer in the blood or determine the damage to tissues in the body caused by cancer. A sample of blood is obtained by temporarily inserting a sterile needle into a vein of cleaned skin. The sample of blood is sent to special laboratories and results may take several minutes or up to weeks to return. Examples of common blood tests include:
- Complete blood count (CBC) examines the number of red blood cells which carry oxygen to the body, the number and type of white blood cells that fight infection, and the number of platelets that help the blood to clot. Sometimes this test will show leukemia cells, which are cancerous, abnormal white blood cells that do not fight infection.
- Complete metabolic or chemistry panel shows how well the liver and kidney are working and whether there are abnormal chemical substances from cancer cells breaking down.
- Tumor biomarkers are special substances that certain types of cancers secrete into the bloodstream. Different tumor biomarkers help to determine different types of cancers and help determine whether a cancer still exists during or after treatment.
- Urine tests. Urine tests help look for kidney and/or bladder damage from cancer cells or tumor biomarkers, special substances that certain cancers secrete into the urine. A sample of urine is obtained by having a child urinate into a special plastic container or bag. The urine sample is sent to special laboratories and results may take minutes to days to return.
Imaging studies help look for cancer in and around normal tissues in the body. Different kinds of pictures are made from different machines using different techniques to look at different parts of the body. A special technician is needed to take the picture of the cancerous tissue in the affected body part that is held still for a given amount of time. Examples of common imaging studies include:
- Plain radiography or X-rays use ionizing radiation in one direction, for a few seconds like a camera to make a picture of the chest, abdomen, pelvis, and/or bones.
- Ultrasonography or ultrasound use sound waves with a wand placed on moisturized skin, for several minutes, to make a picture of the skin, and soft tissues of the neck, breast, abdomen, and/or pelvis.
- Computerized tomography or CT scans use ionizing radiation from a noisy, donut-shaped machine moving along a child who is lying down for several minutes, to make a three-dimensional picture of any part of the body (brain, head, neck, chest, abdomen, pelvis, spine, arms, and/or legs). Sometimes special dye is injected into the bloodstream before the scan to better tell normal tissue from cancer.
- Magnetic Resonance Imaging or MRI scans use magnetic fields from a noisy, tube-shaped machine in which the child lies still for several minutes, to make a three-dimension picture of any part of the body (brain, head, neck, chest, abdomen, pelvis, spine, arms, and/or legs). Special dye is injected before the MRI scan to better tell normal tissue from cancer.
- Positron Emission Tomography or PET scans require injection of a mildly radioactive special dye into the bloodstream which goes to very actively dividing cells (including cancers). The ionizing radiation is detected by a noisy, donut-shaped scanning machine moving along a child who is lying down still for several minutes. This may be combined with a CT scan to create a three-dimensional picture of the entire body that allows cancer to be better distinguished from normal tissue.
- Bone scans involve injection of a temporary radioactive substance that has charged particles, into the blood stream, which only goes to inflamed, damaged or abnormal bone, which is detected by a special scanning machine that takes a picture of the body and helps to better tell normal bone from cancer.
- Meta-iodobenzylguanidine or MIBG scans require an injection of a temporary radioactive substance into the blood stream, which is only taken up by some cancers involving nerve tissue such as pheochromocytoma and neuroblastoma. This is detected by a special scanner that creates a picture of the body, allowing cancer to be distinguished from normal tissue.
Tumor sampling studies may include:
- Tumor biopsy. After a child is given anesthesia or sedation, which causes temporary sleep and relieves any pain, a surgeon operates on the part of the child’s body where the tumor is located. After removing the cancerous tissue, the surgeon closes the wound with special stitches called sutures, a gauze dressing is applied, and a child is woken up. Sometimes the cancer tissue can be sampled using a needle. If cancer is present in a lymph node, one of hundreds of glands that provide infection-fighting fluid throughout the body, the abnormal node also can be removed with surgery or sampled with a needle.
The cancer tissue sample or lymph node sample is sent to a pathologist, a doctor who examines the tissue microscopically to determine the specific type of cancer. Other tests may be done that include flow cytometry to look for abnormal protein markers on the surface of cancer cells, or special genetic testing to look for tumor biomarkers and mutations in the DNA that determine the sub-type of cancer.
- Bone marrow aspirate and biopsy tests for cancer in the marrow, the core part of the bone where red blood cells, white blood cells, and platelets are made. The child is given anesthesia and a sterile needle is temporarily inserted into the rear pelvic bone to remove a small sample of the liquid marrow. In addition, a small piece of solid marrow (about the size of an inch-long string) is also removed. After the needle is removed, a gauze dressing is applied to the skin puncture site. The area may feel sore for a day or two.
The bone marrow samples are sent for special microscope testing to look for any cancer cells; cytogenetic testing to look for any abnormal chromosomes found in cancer cells; flow cytometry to look for abnormal protein markers on the surface of cancer cells; and/or special genetic testing with polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) to look for abnormal DNA in cancer cells.
- Lumbar puncture tests for cancer in the cerebrospinal fluid, the special liquid around the brain and spinal cord that keeps the central nervous system healthy. The child is given anesthesia and a sterile needle is temporarily inserted into the skin, between the 2 bones of the lower back or lumbar vertebrae into the spinal column where the spinal fluid flows. The spinal fluid drips from the needle into special containers. After the needle is removed, a gauze dressing is applied to the skin puncture site. To avoid a headache, the child lies flat for at least 30 minutes afterwards.
The cerebrospinal fluid is sent for special microscopic testing to look for cancer cells. It may also be sent for special chemistry testing looking for tumor biomarkers, and/or flow cytometry testing to look for abnormal proteins on the surface of cancer cells.
Which tests are used for which types of cancers?
Here are four basic categories of cancers which have many cancer sub-types within each category. Different sub-types of cancers require different specialized tests.
Leukemia is the growth of abnormal white blood cells in the bone marrow (soft core of the bones) and bloodstream. Common tests used to diagnose leukemia include:
- Blood tests such as complete blood count and complete metabolic panel
- Bone marrow aspirate and biopsy, and lumbar puncture
Lymphoma is the growth of abnormal white blood cells in the lymph nodes. Common tests used to diagnose lymphoma include:
- Blood tests such complete blood count and complete metabolic panel
- Imaging studies such as X-ray, CT scan, MRI scan and/or PET scan
- Tumor biopsy such as lymph node biopsy, and bone marrow aspirate and biopsy, and lumbar puncture
Brain and spine tumors are the growth of abnormal nerve tissue or abnormal nerve-supporting tissue in the brain and/or spinal cord also known as the central nervous system (CNS). Common tests used to diagnose CNS tumors include:
- Imaging studies such as CT scan, MRI scan, and sometimes Bone scan
- Tumor biopsy by a neurosurgeon (brain surgeon)
- Lumbar puncture
Solid tumors are cancerous growths of abnormal tissues that are not in the bone marrow, lymph nodes, brain or spinal cord. Some examples of different solid tumors include neuroblastoma (cancer of the adrenal gland), Wilms tumor (cancer of the kidney), rhabdomyosarcoma (cancer of the muscle), osteosarcoma (cancer of the bone), Ewing sarcoma (cancer of the bone), hepatoblastoma (cancer of the liver), and germ cell tumor (cancer of the ovaries or testes).
- Blood tests such as complete blood count, complete metabolic panel, and tumor biomarkers
- Urine tests for tumor biomarkers
- Imaging studies such as X-ray, CT scan, MRI scan, PET scan, Bone scan, and/or MIBG scan
- Tumor biopsy such as cancer tissue biopsy, lymph node biopsy, and bone marrow aspirate and biopsy