Diagnosing Retinoblastoma

Retinoblastoma is a rare cancer that can occur in one or both eyes. In this condition, a tumor forms in the retina, the light-sensitive layers of tissue that line the inside of the eye. The retina is essential to eyesight: it sends information through the optic nerve to the brain so that images can be perceived. This cancer is most common in children ages 1 to 3 and accounts for 3 percent of cancers in children under age 15.

Retinoblastoma occurs when a gene mutation—an alteration in a person’s DNA—causes cells in the retina, called retinoblasts, to grow and multiply uncontrollably. The mutation occurs in a gene called RB1.

Though retinoblastomas can be inherited, most are not. Children with a spontaneous, or nonhereditary, retinoblastoma typically develop a tumor in one eye. Children with the inherited type of retinoblastoma may have tumors in both eyes (bilateral tumors) and are at an increased risk for developing trilateral tumors—retinoblastoma in both eyes and also in the pineal gland of the brain.

Children with bilateral or hereditary retinoblastoma are more likely to develop other types of cancer elsewhere in the body later in life.

Retinoblastoma is most commonly identified by a condition called leukocoria, an absence of the normal red reflex in the eye that causes the pupil to appear white instead of red and is most easily seen when a light is shined into the eyes. For example, you might notice a white pupil in a photograph taken with a flash. Your pediatrician generally checks for this symptom at each well visit.

Less commonly, a child with retinoblastoma may have an eye that is larger than usual, pain or redness in the eye, problems with vision, or strabismus, when the eyes don’t line up in the same direction.

If your child’s doctor suspects retinoblastoma, an ophthalmologist at Hassenfeld Children’s Hospital at NYU Langone who specializes in the treatment of eye tumors examines your child’s eyes. A pediatric oncologist—a doctor who specializes in treating children with cancer—takes a medical history and performs a physical exam. Then he or she orders one or more tests, which can help determine the best treatment plan.

Eye Exam

An ophthalmologist examines the eye using lights and magnifying lenses. During this test, the doctor may use eyedrops to dilate the pupils, the black circles in the center of the eyes. Dilation allows the doctor to get a better view of the retina and the optic nerve with an ophthalmoscope, an instrument for examining the inside of the eye. An ophthalmic oncologist then photographs the inside of the front and the back of each eye.

General anesthesia is typically used to help keep children still during the exam, so that both eyes can be thoroughly evaluated.

Ultrasound

In an ultrasound exam of the eye, sound waves create images of the inside of the eye that your doctor views on a computer screen. The test allows the doctor to see parts of the eye and the orbit, or eye socket, that may not be visible during a dilated eye examination, and to measure the size of any tumors found.

Prior to the test, eyedrops are used to numb the eye. During the exam, a probe that transmits sound waves is gently placed on the eye. Sedation is typically required for young children.

MRI Scans

An MRI uses magnetic fields and radio waves to create images of the eye, brain, and other areas of the body. MRI helps the doctor see soft tissues of the eye and orbit and can reveal whether a tumor has spread beyond the eye or eyes and into the orbit or optic nerve.

CT Scans

With a CT scan, a series of X-rays create detailed, three-dimensional images of the eyes, brain, and other organs and tissues. A CT scan can reveal whether cancer has spread to the brain, spinal cord, or other parts of the body. It can also identify the presence of calcium deposits, which commonly collect in retinoblastoma tumors.

Bone Scan

Used when the cancer is at high risk for spreading, a bone scan enables a doctor to look for cancer cells that have spread to the bone. Thirty minutes before the scan, a small amount of radioactive material is injected into a vein in the arm. It travels to the bloodstream, making areas of bone damage more visible on the computer screen during the test. The child lies on a table while a special camera takes images of the bones through the skin in this 30-minute test. Sedation is used to keep children still during the scan.

Genetic Testing

Doctors can use tumor samples collected during surgery or a blood test to look for mutations, or changes, in the gene RB1. This gene is the blueprint for a tumor suppressor protein present in cells in the eye and in tissues elsewhere in the body. Where on the gene this mutation occurs and whether it’s present at birth determine whether a child has the inherited form of retinoblastoma, which increases the risk of new tumors developing after treatment.

The results of genetic testing not only affect the treatment for retinoblastoma but may also indicate the risk for this cancer in the child’s family members.

At NYU Langone’s Clinical Genetic Services, specialists provide personalized information about genetic test results and their implications for your child’s cancer treatments and screening as well as for your future pregnancies. Test results can help determine whether family members should consider their own genetic testing.