Retinoblastoma: CT and MRI

Epidemiology, Diagnosis and Genetics of Retinoblastoma: ICMR Consensus Guidelines

Retinoblastoma (RB) is the most common intraocular tumor in childhood. It is mainly caused by mutations in both alleles of the RB1 tumor suppressor gene that is found on chromosome 13 and regulates the cell cycle. Approximately 8000 children are diagnosed with RB globally each year, with an estimated 1500 cases occurring in India. The survival rate of RB has improved to more than 90% in the developed world. Leukocoria and proptosis are the most common presenting features of RB in Asian Indian populations. Most cases of RB are diagnosed by fundus examination followed by ultrasound. The International Classification of Retinoblastoma is the most used scheme for the staging and classification of intraocular RB in India. Prenatal testing and preimplantation genetic testing for RB may be beneficial in high-risk families. Histopathologic risk factors such as massive choroidal invasion and post-laminar optic nerve help in predicting the occurrence of metastasis in children with RB, while presence of microscopic residual disease requires aggressive adjuvant treatment in eyes enucleated for group E RB. The review provides a consensus document on diagnosis and genetics of RB in India.

Point-of-Care Ultrasound Diagnosis of Retinoblastoma in the Emergency Department

An 18-month-old girl presented to the emergency department with the chief complaint of squinting. The right eye demonstrated esotropia, heterochromia, and anisocoria. Ocular point-of-care ultrasound facilitated the rapid diagnosis of retinoblastoma, which was confirmed by computed tomography scan and orbital magnetic resonance imaging.

Retinoblastoma in an Adult

Retinoblastoma is a rare malignant tumor of the retina usually seen in children before 5 years of age. The tumor is extremely rare in adults. We report here an unusual case of retinoblastoma in a 55-year-old adult female who presented to us with an orbital mass at a late stage of the disease. Detailed laboratory investigations and imaging studies could not make a precise diagnosis. The treating ophthalmologist suspected primary intraocular tumor, metastatic carcinoma, malignant melanoma, or lymphoma and referred the patient for fine needle aspiration cytology (FNAC). Cytopathological examination of Giemsa-stained FNAC smear was consistent with that of retinoblastoma and established the diagnosis.

Retinoblastoma

Retinoblastoma is the most common neoplasm of the eye in childhood, and represents 3% of all childhood malignancies. Retinoblastoma is a cancer of the very young; two-thirds are diagnosed before 2 years of age and 95% before 5 years. Retinoblastoma presents in 2 distinct clinical forms: (1) a bilateral or multifocal, heritable form (25% of all cases), characterized by the presence of germline mutations of the RB1 gene; and (2) a unilateral or unifocal form (75% of all cases), 90% of which are nonhereditary. The treatment of retinoblastoma is multidisciplinary and is designed primarily to save life and preserve vision.

Detection of calcifications in retinoblastoma using gradient-echo MR imaging sequences: comparative study between in vivo MR imaging and ex vivo high-resolution CT

BACKGROUND AND PURPOSE

Intratumoral calcifications are very important in the diagnosis of retinoblastoma. Although CT is considered superior in detecting calcification, its ionizing radiation, especially in patients with hereditary retinoblastoma, should be avoided. The purpose of our study was to validate T2*WI for the detection of calcification in retinoblastoma with ex vivo CT as the criterion standard.

MATERIALS AND METHODS

Twenty-two consecutive patients with retinoblastoma (mean age, 21 months; range, 1-71 months) with enucleation as primary treatment were imaged at 1.5T by using a dedicated surface coil. Signal-intensity voids indicating calcification on T2*WI were compared with ex vivo high-resolution CT, and correlation was scored by 2 independent observers as poor, good, or excellent. Other parameters included the shape and location of the signal-intensity voids. In 5 tumors, susceptibility-weighted images were evaluated.

RESULTS

All calcifications visible on high-resolution CT could be matched with signal-intensity voids on T2*WI, and correlation was scored as excellent in 17 (77%) and good in 5 (23%) eyes. In total, 93% (25/27) of the signal-intensity voids inside the tumor correlated with calcifications compared with none (0/8) of the signal-intensity voids outside the tumor. Areas of nodular signal-intensity voids correlated with calcifications in 92% (24/26), and linear signal-intensity voids correlated with hemorrhage in 67% (6/9) of cases. The correlation of signal-intensity voids on SWI was better in 4 of 5 tumors compared with T2*WI.

CONCLUSIONS

Signal-intensity voids on in vivo T2*WI correlate well with calcifications on ex vivo high-resolution CT in retinoblastoma. Gradient-echo sequences may be helpful in the differential diagnosis of retinoblastoma. The combination of funduscopy, sonography, and high-resolution MR imaging with gradient-echo sequences should become the standard diagnostic approach for retinoblastoma.

Comparison of the diagnostic value of MR imaging and ophthalmoscopy for the staging of retinoblastoma

PURPOSE

To compare the diagnostic value of magnetic resonance (MR) imaging and ophthalmoscopy for staging of retinoblastoma.

METHODS

MR and ophthalmoscopic images of 36 patients who underwent enucleation were evaluated retrospectively following institutional review board approval. Histopathology being the standard of reference, the sensitivity and specificity of both diagnostic modalities were compared regarding growth pattern, iris neoangiogenesis, retinal detachment, vitreous seeds and optic nerve invasion. Data were analysed via McNemar's test.

RESULTS

Both investigations showed no significant difference in accuracy for the detection of different tumour growth patterns (P = 0.80). Vitreous seeding detection was superior by ophthalmoscopy (P < 0.001). For prelaminar optic nerve invasion, MR imaging showed similar sensitivity as ophthalmoscopy but increased specificity of 40 % (CI 0.12-0.74) vs. 20 % (0.03-0.56). MR detected optic nerve involvement past the lamina cribrosa with a sensitivity of 80 % (0.28-0.99) and a specificity of 74 % (0.55-0.88). The absence of optic nerve enhancement excluded histopathological infiltration, but the presence of optic nerve enhancement included a high number of false positives (22-24 %).

CONCLUSIONS

Ophthalmoscopy remains the method of choice for determining extent within the globe while MR imaging is useful for evaluating extraocular tumour extension. Thus, both have their own strengths and contribute uniquely to the staging of retinoblastoma.

KEY POINTS

• Ophthalmoscopy: method of choice for determining extent of retinoblastoma within the globe. • MR imaging provides optimal evaluation of extrascleral and extraocular tumour extension. • Positive enhancement of the optic nerve on MRI does not necessarily indicate involvement.

Guidelines for imaging retinoblastoma: imaging principles and MRI standardization

Retinoblastoma is the most common intraocular tumor in children. The diagnosis is usually established by the ophthalmologist on the basis of fundoscopy and US. Together with US, high-resolution MRI has emerged as an important imaging modality for pretreatment assessment, i.e. for diagnostic confirmation, detection of local tumor extent, detection of associated developmental malformation of the brain and detection of associated intracranial primitive neuroectodermal tumor (trilateral retinoblastoma). Minimum requirements for pretreatment diagnostic evaluation of retinoblastoma or mimicking lesions are presented, based on consensus among members of the European Retinoblastoma Imaging Collaboration (ERIC). The most appropriate techniques for imaging in a child with leukocoria are reviewed. CT is no longer recommended. Implementation of a standardized MRI protocol for retinoblastoma in clinical practice may benefit children worldwide, especially those with hereditary retinoblastoma, since a decreased use of CT reduces the exposure to ionizing radiation.

A magnetic resonance imaging diagnostic dilemma: diffuse infiltrating retinoblastoma versus Coats' disease

A 6-year-old boy presented with neovascular glaucoma secondary to total retinal detachment. Magnetic resonance imaging findings suggested diffuse infiltrating retinoblastoma. Enucleation was subsequently performed and led to a final histopathological diagnosis of advanced Coats' disease. Diffuse infiltrating retinoblastoma and advanced Coats' disease can be indistinguishable from each other on magnetic resonance imaging.

Is CT still useful in the study protocol of retinoblastoma?

BACKGROUND AND PURPOSE

Intralesional calcium deposition is considered a key element for differentiating retinoblastoma from simulating lesions. Our aim was to assess whether MR imaging associated with ophthalmologic investigations (ophthalmoscopy and ultrasonography) could replace CT in the detection of diagnostic intralesional calcifications in retinoblastoma.

MATERIALS AND METHODS

Ophthalmoscopic findings, MR images, CT scans, and histologic examination of 28 retinoblastomas from 23 consecutive children (11 males, 12 females; age range at admission, 1-35 months; mean age, 11 months; median age, 9 months) were retrospectively evaluated. Ultrasonography was performed in 18 patients with 21 retinoblastomas. MR imaging included T2-weighted spin-echo and gradient-echo images, fluid-attenuated inversion recovery images, and T1-weighted spin-echo images with and without contrast enhancement. Clinical data were integrated with MR imaging data to evaluate the utility of both approaches to discover calcifications; particularly, a correlation between intralesional signal-intensity void spots on MR imaging and hyperattenuating areas on CT scans was performed.

RESULTS

Ophthalmoscopy detected calcifications in 12 of 28 eyes (42.85%). Ultrasonography detected calcifications in 20 of 21 eyes (95.23%). CT showed hyperattenuating intralesional areas consistent with calcifications in 27 of 28 eyes (96.42%). MR imaging showed intralesional signal-intensity void spots in 25 of 28 eyes (89.28%). All spots detected with MR imaging matched the presence of calcifications on CT scans. Gradient-echo T2*-weighted and fast spin-echo T2-weighted images showed the highest degree of correlation with CT. When we put together ophthalmoscopy, ultrasonography, and MR imaging data, no calcifications detected on CT were missed, and the differential diagnosis was thorough.

CONCLUSIONS

A combination of clinical data and MR images may remove potentially harmful ionizing radiation from the study protocol of retinoblastoma.

Global issues and opportunities for optimized retinoblastoma care

The RB1 gene is important in all human cancers. Studies of human retinoblastoma point to a rare retinal cell with extreme dependency on RB1 for initiation but not progression to full malignancy. In developed countries, genetic testing within affected families can predict children at high risk of retinoblastoma before birth; chemotherapy with local therapy often saves eyes and vision; and mortality is 4%. In less developed countries where 92% of children with retinoblastoma are born, mortality reaches 90%. Global collaboration is building for the dramatic change in mortality that awareness, simple expertise and therapies could achieve in less developed countries.

Retinoblastoma - MR appearance using a surface coil in comparison with histopathological results

PURPOSE

The purpose of this work was to evaluate the characteristic appearance of untreated retinoblastoma on a large sample in comparison to the histological findings after therapeutical enucleation.

MATERIALS AND METHODS

In a prospective clinical trial 46 children with retinoblastoma in 63 affected untreated eyes were examined under general anesthesia on MRI using a 1.5-T system. The examinations were performed with a special surface coil applying an examination protocol including fast T2- and T1-weighted spin echo sequences and additional fast T1-WI after intravenous injection of Gd-DTPA in different planes. The imaging results were compared to the histopathological findings in 29 patients with 30 affected eyes.

RESULTS

Comparing MRI findings and histopathological results, optic nerve infiltration was detected with a sensitivity of 53.8% and a specificity of 82.3% on MRI, infiltration of the choroid with a sensitivity of 75.0% and a specificity of 100.0%, and the degree of tumor calcification with a sensitivity of 91.7% and a specificity of 88.9%. In this study the characteristic MR appearance of untreated retinoblastoma was evaluated.

CONCLUSION

MRI was helpful in relevant aspects of pretherapeutical retinoblastoma staging, deficits remain regarding optic nerve infiltration.

CT and MRI features of recurrent tumors and second primary neoplasms in pediatric patients with retinoblastoma

OBJECTIVE

The aim of our study was to describe the CT and MRI findings of recurrent tumors and second primary (malignant and benign) neoplasms in patients with retinoblastoma and to evaluate imaging features to assist in distinguishing them.

MATERIALS AND METHODS

Records of 445 pathologically confirmed retinoblastomas were retrospectively reviewed. Thirty-four patients with recurrent retinoblastomas and 15 patients with second primary neoplasms who underwent CT and MRI were evaluated by two radiologists with agreement by consensus.

RESULTS

Invasive patterns of recurrent tumors included type A, intraocular tumor (n = 13); type B, intraorbital tumor with spread into the optic nerve shown as enlargement and marked enhancement of the optic nerve on contrast-enhanced CT or MRI (n = 6); and type C, tumor extending to the lateral aspect of the orbit and invading the brain via the sphenoidal bone (n = 2). Thirty-eight percent of patients with recurrent tumors had distant metastases (n = 7) or leptomeningeal metastases (n = 6). Leptomeningeal metastases were found only in recurrent tumors. Second primary neoplasms included osteosarcoma (n = 5), rhabdomyosarcoma (n = 5), meningioma (n = 4), and other tumors (n = 3). A significant difference was seen between the patients' ages at the time of diagnosis of recurrent tumors and second primary neoplasms (p < 0.0001). Extraorbital tumors were found more frequently among second primary neoplasms than among recurrent tumors (p < 0.001).

CONCLUSION

Both recurrent tumors and second primary neoplasms in patients with retinoblastoma often show characteristic imaging features. The tumor distribution on CT and MRI may help in differentiating recurrent tumors and second primary neoplasms.

High resolution magnetic resonance imaging of retinoblastoma

BACKGROUND/AIMS

Diagnosis of retinoblastoma is mainly based on indirect ophthalmoscopy, but additional imaging techniques are indispensable for the staging of the disease. A new high resolution magnetic resonance imaging (MRI) technique for the examination of the eye was evaluated. A new surface coil with a diameter of 5 cm allows a field of view of 60 mm with an in-plane resolution of 0.8 mm. We compared preoperative MRI scans with the histology after enucleation in 21 cases of retinoblastoma. Parameters studied were appearance of retinoblastoma, choroidal and scleral infiltration, extraocular extension, optic nerve infiltration, and vitreous seeding.

RESULTS

All retinoblastomas could be visualised as hypointense to vitreous on T2 weighted images and slightly hyperintense to vitreous on plain T1 weighted images with a moderate enhancement after contrast application. Histology revealed seven cases with infiltration of the optic disc or optic nerve. Preoperative MRI scans depict juxtapapillary tumour masses, but it was impossible to differentiate between a juxtapapillary retinoblastoma, a prelaminar infiltration of the optic disc, or a just postlaminar optic nerve infiltration. In five of 14 cases with a proved tumour infiltration of the choroid, MRI scans showed an inhomogeneous contrast enhancement of the choroid in enhanced T1 weighted sequences beneath the retinoblastoma. Whether this sign is specific for a choroidal infiltration or is just an artefact remains unclear. High resolution MRI scans did not allow the exclusion of this form of intraocular tumour extension. All nine cases with proved vitreous seeding were not detected by MRI scans. None of these cases showed scleral infiltration or orbital tumour extension. Therefore, it is not possible to judge the rank of this technique in detecting orbital tumour growth.

CONCLUSION

The new MRI technique is of limited value in visualisation of prelaminar or postlaminar infiltration of the optic nerve. Advanced choroidal infiltration might be visualised by contrast enhanced T1 weighted MRI scans, but the available spatial resolution did not allow the exclusion this critical form of tumour growth by MRI scans. Nevertheless, high resolution MRI with the new surface coil has superior contrast and spatial resolution compared to computed tomograph (CT) or other available imaging techniques. MRI cannot replace CT in detecting tumour calcification but with increasing experience with this new technique it should be possible to renounce CT scans in the majority of cases of retinoblastoma.

Retinoblastoma in older children

PURPOSE

Retinoblastoma (RB) is known to present with atypical signs and symptoms in older patients. Our article reviews the clinical and histopathological features of RB encountered in children older than 5 years of age.

METHODS

A total of 337 consecutive patients with RB were reviewed. Eighteen (5.3%; 10 males, 8 females) who presented after the age of 5 were selected for further analysis of clinical data and histopathological material in this retrospective, non-comparative case series.

RESULTS

The age range was from 5 to 12 years (mean age 6.4). Unilateral disease was seen in 14 children, bilateral disease in 4 children. Eleven children were the product of consanguineous marriages. Seven patients had leukocoria; the others presented with signs of uveitis, cellulitis, and/or trauma. Three patients had flat, plaque-like lesions on histopathologic evaluation.

CONCLUSIONS

Clinical and histopathologic features were atypical in 47% and 21% respectively in the retinoblastoma patients who presented after the age of 5 years.

Echography of retinoblastoma: histopathologic correlation and serial evaluation after globe-conserving radiotherapy or chemotherapy

PURPOSE

To assess the sensitivity of echography in detecting retinoblastoma, compare tumor features observed by echography with histopathology data, and assess the usefulness of echography in serially following retinoblastoma tumors after globe-conserving treatments.

METHODS

The medical and echography records of all patients treated for retinoblastoma at the Bascom Palmer Eye Institute between 1991 and 1997 were reviewed. All eyes underwent pretreatment echographic evaluation, and eyes treated with external beam radiotherapy, brachytherapy, or chemotherapy underwent serial follow-up echography.

RESULTS

Sixty-nine eyes of 48 patients were identified. Echography demonstrated evidence of retinoblastoma in 69 of 69 (100%) eyes and calcification in 63 (91.3%) eyes. Histopathology was superior to echography in detecting optic nerve invasion, extraocular extension, and presence of calcification.

CONCLUSION

Echography is a useful adjunct to indirect ophthalmoscopy in establishing the diagnosis of retinoblastoma. While not as specific as histopathology, echographic evaluation before and after treatment of retinoblastoma permits monitoring of treatment response and may aid in detecting recurrent tumor growth or failure to respond to treatment.

Coats' disease and persistent hyperplastic primary vitreous. Role of MR imaging and CT

Coats' disease is an idiopathic disorder in which telangiectatic and aneurysmal retinal vessels leak a lipoproteinaceous exudate, with consequent bullous retinal detachment. It is a diagnostic challenge, and CT and MR imaging provide valuable information to differentiate it from other pathologies, particularly from retinoblastoma. Typical, advanced Coats' disease shows on CT a denser substance posterior to the vitreous, which on MR is hyperintense on all pulse sequences. Contrast administration on both CT and MR might give slight linear enhancement at the boundary between vitreous and exudation. Persistent hyperplastic primary vitreous (PHPV) is a unilateral disorder in a microphthalmic eye, seen in full-term infants. PHPV rarely is bilateral in patients with Norrie's disease, Warburg syndrome, or patients with retinal dysplasia. Persistent fetal vasculature leads to fibrosis, resulting in elongation of the ciliary processes, retinal detachment, and spontaneous cataracts. The CT appearance in the disorder is quite variable; however, MR imaging may be superior in demonstrating the enhancing retrolental mass and the elongated ciliary processes.

Detection of optic nerve involvement in retinoblastoma with enhanced computed tomography

PURPOSE

The study was designed to evaluate the value of enhanced computed tomography (CT) as a non-invasive test in the detection of optic nerve invasion in retinoblastoma.

METHODS

Nineteen eyes in 17 consecutive retinoblastoma patients underwent CT studies performed with high spatial resolution (512 x 512) and 1.5 mm sections, both with enhancement and without enhancement. If the central retinal vessels (CRV) were subjectively visualised with intravenous enhancement, the optic nerve was considered to be free of retinoblastoma. Nineteen enucleated globes were processed for histopathology, and the optic disc and nerve examined with light microscopy for the presence or absence of tumour and the level of involvement.

RESULTS

The correlation between the visualisation of CRV and the presence or absence of optic nerve involvement histopathologically was found to be highly significant (p = 0.0006, Fisher exact test).

CONCLUSION

In high spatial resolution CT with enhancement and 1.5 mm or thinner sections, non-visualisation of the CRV appears to be a reliable indicator of optic nerve invasion with retinoblastoma.

MR imaging in retinoblastoma

We studied the appearance of retinoblastoma on unenhanced and gadolinium-enhanced images and the accuracy of tumour staging with MR imaging. The MR images were obtained in 18 children with retinoblastoma and compared with histopathological findings after enucleation. The MR imaging included T1-weighted and dual-echo T2-weighted images before, and T1-weighted images after, gadopentetate dimeglumine injection. The contrast between tumour and ipsilateral vitreous strongly increased (57 %) after gadolinium on T1-weighted images (p = 0.004). Tumour was strongly hypointense as compared with ipsilateral vitreous in all patients using heavily T2-weighted (TE = 120 ms) images (p = 0.001). The estimated T2 of tumour (mean 96 + 14 ms) did not correlate with histological grading or degree of calcification. Unenhanced T1-weighted MR images rightfully excluded extrascleral growth in 16 of 16 cases, but its presence was confirmed after enucleation in only one of 2 abnormal MR scans. Invasion of the optic nerve behind the cribriform plate was confirmed in 2 of 3 abnormal gadolinium-enhanced MR scans, but also in 1 of the 15 cases in which MR images were normal. The T2-weighted images were useful in assessing retinal detachment. We conclude that heavily T2-weighted images, unenhanced T1-weighted images and gadolinium-enhanced T1-weighted MR images are complementary in characterizing and staging retinoblastoma.

Imaging in the trilateral retinoblastoma syndrome

The medical records, CT, and MRI of ten children with trilateral retinoblastoma were reviewed. The intracranial pathology consisted of eight pineal neoplasms and two parasellar lesions, at least seven of the which were calcified. Two lesions demonstrated calcification only (no soft tissue mass) at initial presentation. Hydrocephalus was seen in eight cases, and concurrent or subsequent subarachnoid dissemination was documented in seven. Only one patient is known to be alive at the present time. The imaging features of the midline intracranial tumors mirror those of the ocular neoplasm. As calcification may be the only clue to the presence of the intracranial malignancy, close surveillance of high-risk patients with retinoblastoma with initial CT and follow-up MRI is suggested.

Efficacy of unanesthetized spiral computed tomography scanning in initial evaluation of childhood leukocoria

PURPOSE

To evaluate the use of spiral/helical computed tomography (CT) in the preoperative evaluation of pediatric leukocoria.

METHODS

A total of 34 patient charts and imaging studies were reviewed from a consecutive series of children referred with the diagnosis of presumed retinoblastoma. Of these patients, 31 had a confirmed diagnosis of retinoblastoma. Three patients had simulating lesions, including one patient with persistent hyperplastic primary vitreous and two with Coats disease.

RESULTS

In all patients, a diagnosis of intraocular retinoblastoma could be established or excluded at the same clinical level by spiral CT as by conventional CT. Spiral CT of the eye, orbit, and midline structures was performed without a requirement for patient anesthesia. This technique resulted in a reduced volume of contrast material required for evaluation of the central nervous system and a small decrease in total radiation exposure. There was an attendant reduction in the amount of monitoring equipment required and the necessity for attending anesthesia staff.

CONCLUSIONS

The primary advantage of spiral CT is reduced anesthesia risk in small children. In addition, this technique provides necessary clinical information with a reduction in image acquisition time, monitoring equipment, and monitoring staff.