Retinoblastoma - Childhood: Diagnosis

Approved by the Cancer.Net Editorial Board, 09/2022

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find the cause of a medical problem. Use the menu to see other pages.

Doctors use many tests to find, or diagnose, cancer. They also do tests to learn if cancer has spread to another part of the body from where it started. If the cancer has spread, it is called metastasis. Doctors may also do tests to learn which treatments could work best.

For most types of cancer, a biopsy is the only sure way for the doctor to know if an area of the body has cancer. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory. However, the diagnosis process is different for retinoblastoma. A diagnosis for retinoblastoma is never made by a biopsy when the tumor is confined to the eye or eyes. Instead, the diagnosis of retinoblastoma is made after a detailed examination of the affected eye or eyes by an experienced ophthalmologist. 

How retinoblastoma is diagnosed

There are many tests used for diagnosing retinoblastoma. Not all tests described here will be used for every person. Your child's doctor may consider these factors when choosing a diagnostic test:

  • The type of cancer suspected

  • Your child's signs and symptoms

  • Your child's age and general health

  • The results of earlier medical tests

The next step after observing any symptoms (see Symptoms and Signs) is to have the child examined by a specialist, who will do a thorough ophthalmic examination to check the retina for a tumor. Depending on the child’s age, either a local or general anesthetic is used during the eye examination. Anesthetic is a medication that blocks the awareness of pain.

The specialist will make a drawing or take a photograph of the tumor in the eye to provide a record for future examinations and treatment. Additional tests may also be done to locate or confirm the presence of a tumor.

In addition to a physical examination, the following tests may be used to diagnose retinoblastoma:

  • Ultrasound. An ultrasound uses sound waves to create pictures of the internal organs. A transmitter that emits sound waves is moved over the child’s body. A tumor generates different echoes of the sound waves than normal tissue does, so when the waves are bounced back to a computer and changed into images, the doctor can locate a mass inside the body. The procedure is painless.

  • Computed tomography (CT or CAT) scan. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A computer combines these pictures into a detailed, 3-dimensional image that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size or help the doctor find cancer outside of the eye. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow. CT scans are used less commonly in diagnosing retinoblastoma because of the concern raised by the radiation associated with this type of scan.

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the brain and spinal column. MRI can also be used to measure the tumor’s size. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow. An MRI is increasingly recommended because it avoids the radiation associated with CT scans and better shows the structures of the eye, orbit, and brain.

  • MRI or CT scan of the brain. These tests may be recommended to find out if there is an abnormality of the pineal gland, which is a small gland in the brain that regulates the body’s response to light. It is recommended that these scans be performed once every 6 months until age 5 for children with the genetic form of retinoblastoma, which includes those with bilateral disease and those with unilateral disease who have a family history of the disease. Very young children with a tumor in 1 eye who do not have a family history of the disease may also be at risk, and these tests may be recommended. Scans may also be recommended years after treatment for children who have received external-beam radiation therapy (see Types of Treatment), either as a baseline in case of problems in the future or to determine the cause of a new symptom or sign of a problem.

If there are any additional signs found during the physical examination, the doctor may recommend more tests to determine if the cancer has spread elsewhere in the body.

  • Blood tests. These tests evaluate the blood and check for problems with the liver and kidneys. The doctor may also look at the blood for changes in chromosome 13. Chromosomes are the parts of a cell that contain genes. In a few cases of retinoblastoma, these genes are either missing or nonfunctional. Molecular analysis of the gene is now possible in a few medical centers to determine changes that are not visible on an ordinary chromosome analysis.

  • Lumbar puncture (spinal tap). A lumbar puncture is a procedure in which a needle is used to take a sample of cerebral spinal fluid (CSF) to look for cancer cells, blood, or tumor markers, which are substances found in higher than normal amounts in the blood, urine, or body tissues of people with certain kinds of cancer. CSF is the fluid that flows around the brain and the spinal cord. Doctors generally give an anesthetic to numb the child’s lower back before the procedure.

  • Bone marrow aspiration and biopsy. These 2 procedures are similar and often done at the same time to examine the bone marrow. Bone marrow is the spongy, fatty tissue found inside larger bones that produces blood cells. Bone marrow has both a solid and a liquid part. A bone marrow aspiration removes a sample of the fluid with a needle. A bone marrow biopsy is the removal of a small amount of solid tissue using a needle.

    A pathologist then analyzes the sample(s). A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease. A common site for a bone marrow aspiration and biopsy is the pelvic bone, which is located in the lower back by the hip. Doctors generally give anesthesia beforehand to numb the area and to lessen the pain.

  • Hearing test. Children with retinoblastoma receiving specific types of chemotherapy (see Types of Treatment) may have their hearing tested to make sure the drugs are not causing hearing loss. This may also be called an audiology test.

Learn more about preparing your child for medical tests.

After diagnostic tests are done, your child's doctor will review the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer. This is called staging.

The next section in this guide is Stages. It explains the system doctors use to describe the extent of the disease. Use the menu to choose a different section to read in this guide.