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.[1, 2, 3]
(See the image below.)
View Image | Retinoblastoma, glaucomatous stage. History: AB, 2-year-old female from Marikina City, Philippines, with chief complaint of proptosis, right eye. The .... |
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.[4] When a patient with RB develops a pineal tumor, the term trilateral RB (TRB) is used.[5, 6, 7]
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.[8, 9, 10, 11]
(See the image below.)
View Image | Patient with retinoblastoma, glaucomatous stage. Intracranial extension on CT scan. |
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.[2, 12, 13]
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.[14]
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.[15] False-positive results can occur in cases involving other, similar pathologies.
Computed Tomography
On CT scans, RB is seen as a mass that is predominantly located in the posterior ocular pole. The mass may have distinct contours and an inhomogeneous structure, and it may contain calcifications in 70.5% of cases.
CT scanning has high sensitivity in the detection of intraocular tumors, and it has a specificity of 91% for RB. This modality has allowed the staging of intraocular tumors, the detection of extrabulbar growth, and the determination of further treatment approaches. CT scanning can be used to follow up tumors to determine the effect of treatment and to establish a timely diagnosis of malignant tumor relapses.
An epibulbar osseous choristoma can simulate extraocular extension of RB in an eye with an intraocular malignancy; however, the intraocular contents display features typical of RB without extraocular extension.
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.[8, 9, 10, 11]
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is not as specific for diagnosing RB as CT scanning because of MRI's insensitivity for detecting calcium. When calcium is detected, it may be seen as an area of low signal intensity on all pulse sequences.[2] RB is usually visualized as a mass that is slightly hyperintense relative to the vitreous on T1-weighted images and that is hypointense on T2-weighted images. T1 hyperintensity may be due to the presence of melanin. Mild to marked enhancement is seen on gadolinium–enhanced T1-weighted images.
One study compared diagnostic gadolinium-enhanced T1-weighted MRI image quality without and with fat saturation. Thirty-six children (mean age, 19.0 ± 16.8 [SD] months) were included. Image quality and anatomic detail depiction were found to be significantly better without fat saturation, but tumor enhancement was rated higher with fat saturation. Detection of choroidal invasion was improved without fat saturation, but fat saturation improved detection of (post-)laminar optic nerve infiltration. According to the authors, combining both sequences was the best approach in assessing tumor extension (sensitivity and specificity for [post-]laminar optic nerve infiltration were 75% and 100%, respectively; sensitivity and specificity for choroidal invasion were 87.5% and 85.7%, respectively).[12]
Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the topic Nephrogenic Systemic Fibrosis.
Like CT scanning, MRI has a role in the detection of extraocular tumor spread, especially extension into the optic canal.[14, 13] It can also depict intracranial tumors associated with TRB.
Retinal detachment is well depicted on MRI.
Ultrasonography
Three-dimensional (3D) ultrasonography can be used to perform retinal and tumor mapping, which is useful in planning localized or plaque radiation. Subsequently, 3D ultrasonography can also help confirm the proper positioning of such plaques. In addition, calcification and retinal detachment can be diagnosed with this modality; however, 3D ultrasonography is not useful for depicting the extraocular spread of tumors. General anesthesia must be a part of this examination, because the eye should be still during the scan.[16, 17]
Color Doppler imaging reveals slightly vascularized tumor areas and can depict blood flow inside the tumor.[18]
Author
Antonio Pascotto, MD, Consulting Ophthalmologist, Pascotto, Istituto per la Salute degli Occhi, Clinica Mediterranea, Italy
Disclosure: Nothing to disclose.
Coauthor(s)
Jugesh Cheema, MD, Radiologist, Evansville Radiology
Disclosure: Nothing to disclose.
Sergio Claudio Saccà, PhD, Professor of Ophthalmology, Department of Neurological and Visual Sciences, Ospedale San Martino, Italy
Disclosure: Nothing to disclose.
Specialty Editors
Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.
C Douglas Phillips, MD, FACR, Director of Head and Neck Imaging, Division of Neuroradiology, New York-Presbyterian Hospital; Professor of Radiology, Weill Cornell Medical College
Disclosure: Nothing to disclose.
Chief Editor
Eugene C Lin, MD, Attending Radiologist, Teaching Coordinator for Cardiac Imaging, Radiology Residency Program, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine
Disclosure: Nothing to disclose.
Additional Contributors
Charles M Glasier, MD, Professor, Departments of Radiology and Pediatrics, University of Arkansas for Medical Sciences; Chief, Magnetic Resonance Imaging, Vice-Chief, Pediatric Radiology, Arkansas Children's Hospital
Disclosure: Nothing to disclose.
Acknowledgements
Angelo Bartolomeo de Iuri, MD, Radiologist Specialist, Studio Radiologico Bartolomeo De Iuri, Napoli, Italy
Disclosure: Nothing to disclose.
Roberto Bianco, MD Professor of Digestive Surgery and Endoscopy, Milan University, Italy; Complex Structure Director, Section of Radiodiagnostic and Radiotherapeutics, L Sacco Hospital, Milan, Italy
Disclosure: Nothing to disclose.
){kind=link}
){kind=link}