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Retinoblastoma Imaging

Practice Essentials

Retinoblastoma (RB) is a malignant tumor of the developing retina that occurs in children, usually before age 5 years, and may be unilateral or bilateral. It is the most common primary ocular malignancy of childhood. About 60% of patients have unilateral RB, with a mean age at diagnosis of 24 months, and about 40% have bilateral RB, with a mean age at diagnosis of 15 months. Worldwide, the incidence of retinoblastoma is 1 in 16,000 live births.

(See the image below.)

Retinoblastoma, glaucomatous stage. History: AB, 2

Retinoblastoma, glaucomatous stage. History: AB, 2-year-old female from Marikina City, Philippines, with chief complaint of proptosis, right eye. The patient is an adopted child. Prior to admission (PTA), with child aged 6 months (time of adoption), surrogate mother noted an opacity in the right eye. No medical consultation. One year PTA, physician consultation; told AB had an “eye mass” and needed to see an ophthalmologist. No compliance. One month PTA, proptosis was noted in the right eye. Examination: Visual acuity (VA) of right eye is no light perception; VA of left eye is central, steady, and maintained fixation. Sensorium: Awake but irritable. Diagnostics: Intracranial extension on CT scan. Skeletal survey: E/N. Management: The patient underwent exenteration (right side).

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Mutations in the RB gene (long arm of chromosome 13q14) predispose individuals to the disease, as well as to an increased risk of developing pineal tumors, extracranial sarcomas, and melanoma.
When a patient with RB develops a pineal tumor, the term trilateral RB (TRB) is used.

RB may occur sporadically (60%), or it may be inherited (40%). Historically, the RB trait seemed to be transmitted in an autosomal dominant pattern. Occasionally, however, the trait skips a generation in families, indicating genetic carriers.

Preferred examination

The volume of the intraocular tumor is estimated by means of orbital A and B scanning and/or a computed tomography (CT) scanning. On rare occasions, RB is discovered during a well-baby examination. Most often, a parent first detects the symptoms of RB. Cranial and orbital CT provides a sensitive method for diagnosis and detection of intraocular calcification and shows the intraocular extent of the tumor even if calcification is absent.

Optical coherence tomography (OCT), which is based on differential near‐infrared light reflection, has been shown to improve the clinical evaluation of retinoblastoma compared with ultrasound or MRI. Handheld intraoperative OCT has become especially popular for pediatric retinoblastoma assessment.

(See the image below.)

Patient with retinoblastoma, glaucomatous stage. I

Patient with retinoblastoma, glaucomatous stage. Intracranial extension on CT scan.

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MRI may be beneficial in estimating the degree of differentiation of retinoblastomas, but MRI is not as specific as CT because the former lacks sensitivity in detecting calcium. The tumors usually have a low intensity on T1-weighted images and are usually difficult to distinguish from surrounding vitreous. On T2-weighted images, retinoblastoma tumors demonstrate very low intensity compared to vitreous, and calcification is more pronounced on T2 sequences.

De Jong et al concluded that MRI images showed higher diagnostic accuracy than CT for detecting prelaminar optic nerve and choroidal invasion, but the differences were not statistically significant.

Ultrasonography can distinguish retinoblastomas from nonneoplastic conditions and is useful in detecting calcifications.

Retinal fluorescein angiography helps confirm the diagnosis of RB but is not usually performed for this disease because of the availability of noninvasive, cross-sectional imaging methods.
​ False-positive results can occur in cases involving other, similar pathologies.

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