From the archives of the AFIP: Pediatric orbit tumors and tumorlike lesions: neuroepithelial lesions of the ocular globe and optic nerve

Congenital Malformations of the Eye: A Pictorial Review and Clinico-Radiological Correlations

Congenital malformations of the eye represent a wide and heterogeneous spectrum of abnormalities that may be part of a complex syndrome or be isolated. Ocular malformation severity depends on the timing of the causative event during eye formation, ranging from the complete absence of the eye if injury occurs during the first weeks of gestation, to subtle abnormalities if the cause occurs later on. Knowledge of ocular malformations is crucial to performing a tailored imaging protocol and correctly reporting imaging findings. Together with the ophthalmologic evaluation, imaging may help frame ocular malformations and identify underlying genetic conditions. The purpose of this pictorial review is to describe the imaging features of the main ocular malformations and the related ophthalmologic findings in order to provide a clinico-radiological overview of these abnormalities to the clinical radiologist. Sight is a crucial sense for children to explore the world and relate with their parents from birth. Vision impairment or even blindness secondary to ocular malformations deeply affects children's growth and quality of life.

Pigmented medulloepithelioma of the optic nerve: A challenging diagnostic entity

Because of its rarity, the diagnosis of optic nerve medulloepithelioma poses a real diagnostic challenge. Medulloepithelioma is a congenital tumor that derives from the primitive medullary epithelium present in the neural tube and the optic vesicle. Its classical location is the ciliary body. Cases of retinal or optic nerve locations have been rarely reported in the literature. Only 11 cases have been published in the English literature. Herein, we report the case of a 2-year-old boy who underwent enucleation of the right eye for a presumed diagnosis of right-eye retinoblastoma, based on the presence of leukocoria on ophthalmological examination. Pathological examination showed an optic nerve medulloepithelioma. A review of the literature is also discussed in our work.

Neuroimaging of Ocular Abnormalities in Children

In this article, we will discuss the essential MR imaging protocol required for the assessment of ocular abnormalities including malignancies. Then we will describe relevant anatomy, ocular embryogenesis, and genetics to establish a profound understanding of pathophysiology of the congenital ocular malformations. Finally, we will discuss pediatric ocular malignancies, benign mimics, and the most common congenital ocular malformations with case examples and illustrations and give tips on how to distinguish these entities on neuroimaging.

Transorbital neuroendoscopy-assisted resection of a giant optic pathway glioma in a neonate

Congenital giant orbital tumors in infancy are relatively rare, especially when the tumors are associated with significant intracranial extension. We describe the use of a transorbital neuroendoscopy-assisted resection of such a lesion. While this approach is increasingly gaining popularity for certain anterior and middle skullbase lesions in adults, this report represents the youngest patient reported on where this minimally invasive approach has been successfully used to resect the intracranial tumor. This surgical approach obviated the need for a separate craniotomy, with the additional benefit of minimizing blood loss.

Orbital Tumors-Clinical, Radiologic and Histopathologic Correlation

Orbital masses include a broad spectrum of benign and malignant entities. Often these masses are asymptomatic or show a slow growth rate, so that emergence of clinical symptoms is prolonged. In this context, cross-sectional imaging plays an elementary role in the characterization of these lesions. Aside from the characterization of the underlying entity, an evaluation of the involved compartments is possible by sufficient imaging, which also facilitates optimal treatment and surgery planning. The purpose of this review is to explore different benign and malignant orbital tumors and their typical appearance in imaging together with histopathologic findings.

A rare MRI finding of NF-1: perineural arachnoidal gliomatosis

Optic pathway gliomas are the most common central nervous system neoplasms in patients with neurofibromatosis type 1. Perineural arachnoidal gliomatosis is a rare and distinctive growth pattern of optic nerve glioma, in which the tumor infiltrates through the pia mater and pre-dominantly involves the subarachnoid space around the optic nerve. Here, we report an 8-year-old girl with perineural arachnoidal gliomatosis associated with neurofibromatosis type 1.

Guidelines for magnetic resonance imaging in pediatric head and neck pathologies: a multicentre international consensus paper

The use of standardized imaging protocols is paramount in order to facilitate comparable, reproducible images and, consequently, to optimize patient care. Standardized MR protocols are lacking when studying head and neck pathologies in the pediatric population. We propose an international, multicenter consensus paper focused on providing the best combination of acquisition time/technical requirements and image quality. Distinct protocols for different regions of the head and neck and, in some cases, for specific pathologies or clinical indications are recommended. This white paper is endorsed by several international scientific societies and it is the result of discussion, in consensus, among experts in pediatric head and neck imaging.

Eye-sparing Treatment of Localized Orbital Medulloepithelioma With Neoadjuvant Chemoradiation

A 9-year-old girl presented with a 3-day history of progressive proptosis accompanied by transient discomfort and blurry vision in the OD. MRI revealed a heterogeneously enhancing intraconal lesion that partially encased and displaced the optic nerve. There was no intraocular or intracranial involvement, nor were there signs of distant metastasis. Histopathologic evaluation and immunohistochemistry were consistent with orbital medulloepithelioma. The patient received 4 cycles of chemoradiation per a retinoblastoma protocol. Repeat MRI scans showed significant tumor regression, and further surgical debulking was performed. There has been no evidence of recurrence for over 14 months. Herein, the authors describe an eye-sparing, multimodal treatment of a rare case of localized orbital medulloepithelioma.

Retrobulbar embryonal tumor with multilayered rosettes in a golden retriever dog

Although rare, embryonal tumors (previously called primitive neuroectodermal tumors) should be considered in the differential diagnosis of retrobulbar tumors in dogs regardless of the age of the patient, and ancillary tests are required for definitive diagnosis.

Quantitative characterization of extraocular orbital lesions in children using diffusion-weighted imaging

BACKGROUND

Diffusion-weighted imaging (DWI) has been shown to be helpful in providing information about cellular density and also predicting the histological features of aggressive tumors. Several studies have evaluated this technique for orbital tumors. However, very few articles have focused exclusively on evaluating pediatric orbital masses and, within those, only a small number of patients were included in the study.

OBJECTIVE

This study aimed to evaluate the use of DWI and apparent diffusion coefficient (ADC) values to differentiate between benign and malignant extraocular orbital lesions in children.

MATERIALS AND METHODS

This retrospective study included 73 patients under the age of 18 seen in our hospital between October 2016 and February 2019. The extraocular orbital lesions were evaluated clinically and radiologically using DWI. The diagnosis was confirmed by either histological examination (after biopsy or surgery) or based on clinical and radiologic evaluation.

RESULTS

The malignant lesions were found to have increased diffusion restriction in comparison to the benign lesions. The ADC values of the malignant lesions were significantly lower (P<0.0001). The use of a cutoff value of 0.99×10^-3 mm²/s allowed for the differentiation of the benign lesions and malignant lesions with a sensitivity of 75% and a specificity of 100% while the cutoff point of 1.26×10^-3 mm²/s had a sensitivity of 100% and a specificity of 73%.

CONCLUSION

Measurement of ADC in extraocular orbital lesions in children may help differentiate malignant lesions from benign lesions.

MR Imaging Features to Differentiate Retinoblastoma from Coats' Disease and Persistent Fetal Vasculature

Simple Summary

Retinoblastoma is a rare cancer that develops in the retina of children. Accurate differentiation between retinoblastoma and conditions that show similarities with retinoblastoma (pseudoretinoblastoma or retinoblastoma mimickers) is vital for guiding treatment. The most common pseudoretinoblastoma conditions are Coats’ disease and persistent fetal vasculature (PFV). In this study, we aimed to improve pretreatment differentiation between these diseases on MR imaging. We compared pre-treatment MR images of retinoblastoma, Coats’ disease and PFV on 20 predefined MR imaging features. An assessment strategy was proposed incorporating MR imaging features that best differentiate retinoblastoma from pseudoretinoblastoma, including three newly identified MR imaging features.

Abstract

Retinoblastoma mimickers, or pseudoretinoblastoma, are conditions that show similarities with the pediatric cancer retinoblastoma. However, false-positive retinoblastoma diagnosis can cause mistreatment, while false-negative diagnosis can cause life-threatening treatment delay. The purpose of this study is to identify the MR imaging features that best differentiate between retinoblastoma and the most common pseudoretinoblastoma diagnoses: Coats’ disease and persistent fetal vasculature (PFV). Here, six expert radiologists performed retrospective assessments (blinded for diagnosis) of MR images of patients with a final diagnosis based on histopathology or clinical follow-up. Associations between 20 predefined imaging features and diagnosis were assessed with exact tests corrected for multiple hypothesis testing. Sixty-six patients were included, of which 33 (50%) were retinoblastoma and 33 (50%) pseudoretinoblastoma patients. A larger eye size, vitreous seeding, and sharp-V-shaped retinal detachment were almost exclusively found in retinoblastoma (p < 0.001–0.022, specificity 93–97%). Features that were almost exclusively found in pseudoretinoblastoma included smaller eye size, ciliary/lens deformations, optic nerve atrophy, a central stalk between optic disc and lens, Y-shaped retinal detachment, and absence of calcifications (p < 0.001–0.022, specificity 91–100%). Additionally, three newly identified imaging features were exclusively present in pseudoretinoblastoma: intraretinal macrocysts (p < 0.001, 38% [9/24] in Coats’ disease and 20% [2/10] in PFV), contrast enhancement outside the solid lesion (p < 0.001, 30% [7/23] in Coats’ disease and 57% [4/7] in PFV), and enhancing subfoveal nodules (38% [9/24] in Coats’ disease). An assessment strategy was proposed for MR imaging differentiation between retinoblastoma and pseudoretinoblastoma, including three newly identified differentiating MR imaging features.

Intraocular Medulloepithelioma: AIRP Best Cases in Radiologic-Pathologic Correlation

Editor's Note.-RadioGraphics continues to publish radiologic-pathologic case material selected from the American Institute for Radiologic Pathology (AIRP) "best case" presentations. The AIRP conducts a 4-week Radiologic Pathology Correlation Course, which is offered five times per year. On the penultimate day of the course, the best case presentation is held at the American Film Institute Silver Theater and Cultural Center in Silver Spring, Md. The AIRP faculty identifies the best cases, from each organ system, brought by the resident attendees. One or more of the best cases from each of the five courses are then solicited for publication in RadioGraphics. These cases emphasize the importance of radiologic-pathologic correlation in the imaging evaluation and diagnosis of diseases encountered at the institute and its predecessor, the Armed Forces Institute of Pathology (AFIP).

Conservative treatment of diffuse infiltrating retinoblastoma: optical coherence tomography-assisted diagnosis and follow-up in three consecutive cases

Background/aims

To report conservative therapy in diffuse infiltrating retinoblastoma (DIR) and describe specific optic coherence tomography (OCT) features of the tumour.

Methods

Retrospective review of all DIR cases treated conservatively between 1998 and 2012.

Results

Three patients (three eyes) were included, cases 1 and 3 with previous enucleation of the contralateral eye and case 2 with unilateral retinoblastoma referred after prior pars plana vitrectomy with silicone oil. Mean age at diagnosis was 7 years (range 14 months–14 years). Globe and vision preservation (Snellen visual acuity of 12.5/10) was achieved in case 3 with a recurrence-free follow-up of 33 months after first-line thermotherapy followed by salvage intra-arterial chemotherapy (IAC) plus focal treatments. Cases 1 and 2 were enucleated for progressive disease, case 1 after first-line intravenous chemotherapy (IVC) consolidated by focal therapies and salvage treatments given over 8 years of partial remission and case 2 after IAC, brachytherapy and intracameral chemotherapy. Neither showed any high-risk histopathological features, and no adjuvant chemotherapy was necessary. Both patients are alive without metastasis (mean follow-up of >10 years). Pathognomonic features of the tumour were revealed by OCT in all cases, showing infiltration of the ganglion cell layer and horizontal growth over the inner plexiform layer. Complete restoration of the retinal microanatomy was documented after retraction of the tumour following IVC in case 2 and IAC in case 3.

Conclusion

This is the first report of successful conservative management in DIR. OCT enabled diagnosis, delimitation of the tumour margins and monitoring of the treatment response in this context.

Investigation into the quantitative and qualitative characteristics of choroidal melanoma through magnetic resonance imaging and B-scan ultrasound

OBJECTIVE

To investigate the homogeneity and vascularity of choroidal melanoma through magnetic resonance imaging (MRI) and brightness modulation (B-mode) ultrasound scan and their correlation with dimensions of tumor, as well as to measure the sensitivity of both modalities in retinal detachment (RD) detection.

MATERIALS AND METHODS

This retrospective chart review included patients diagnosed with choroidal melanoma. All these patients underwent MRI scans using T2-weighted (T2-WI) and T1-weighted (T1-WI) sequences, before and after an intravenous injection of paramagnetic contrast material. The patients were also examined using a B-mode ultrasound scan, and the results from both modalities were compared (tumor homogeneity, tumor height, tumor base diameter, and tumor vascularity).

RESULTS

Forty-two patients (mean age=65.33±12.51 years) with choroidal melanoma were included in the study. Homogeneity was confirmed in 16 patients through ultrasound scan, in 19 patients through T1-WI sequence, in 21 patients through T2-WI sequence, and in 25 patients through T1-WI sequence + contrast (gadolinium). Patients with homogenous tumors presented with lower (P=0.0045) mean height than that of those with nonhomogenous tumors, whereas no statistically significant difference was found for base diameter measurements (P=0.056). Patients with tumors of high vascularity presented with greater mean height (P=0.000638) and greater mean base diameter compared with those with tumors of low vascularity (P=0.019543). RD was detected in 26 patients through T1-WI sequence, in 13 patients through T2-WI sequence, in 26 patients through T1-WI sequence + contrast, and in 32 patients through ultrasound scan, which proved to be the most sensitive modality.

CONCLUSION

The height of choroidal melanoma was positively correlated with tumor's homogeneity. Melanomas of greater height were found to be less homogenous, due to increased degeneration and higher occurrence of intratumoral hemorrhage. In addition, choroidal melanoma's height was also positively correlated with the level of its vascularity. Finally, ultrasound scan was found to be more sensitive than MRI in the detection of RD.

Imaging of Pediatric Orbital Diseases

This article reviews a variety of congenital and developmental disorders of the pediatric orbit with particular emphasis on ocular lesions, followed by a description of developmental and neoplastic orbital and ocular masses. The relationship of these diseases to various syndromes and/or known genetic mutations is also highlighted.

Cavernous malformation of the optic chiasm: Neuro-endoscopic removal

Cavernous malformations (CMs) arising from the optic nerve and chiasm are extremely rare. In large autopsy series, CMs were estimated to range from 0.02 to 0.13% in the general population. However, with introduction of MRI, these lesions were found more often than previously thought, ranging from 0.2% to 0.4%. Only 29 cases have been reported according to our knowledge. Most patients present with drop in visual acuity and visual field. Although MRI findings of cavernous malformations have been reported, they may not be diagnostic enough. Among the 29 reported, 16 underwent total resection with good results. In some, resection was complicated by damage to the surrounding neural tissue. Surgical removal is the recommended treatment to restore or preserve vision and to eliminate the risk of future hemorrhage. However, the anatomical location and eloquence of nearby neural structures can make these lesions difficult to access and remove. CMs appear to occur in every age group (range 4 months to 84 years mean-34.6 years) ith an approximately equal male to female ratio. They typically present with chiasmal apoplexy, characterized by sudden visual loss, acute headaches, retro orbital pain, and nausea

Orbital tumours and tumour-like lesions: exploring the armamentarium of multiparametric imaging

Although the orbit is a small anatomical space, the wide range of structures present within it are often the site of origin of various tumours and tumour-like conditions, both in adults and children. Cross-sectional imaging is mandatory for the detection, characterization, and mapping of these lesions. This review focuses on multiparametric imaging of orbital tumours. Each tumour is reviewed in relation to its clinical presentation, compartmental location, imaging characteristics, and its histological features. We herein describe orbital tumours as lesions of the globe (retinoblastoma, uveal melanoma), optic nerve sheath complex (meningioma, optic nerve glioma), conal-intraconal compartment (hemangioma), extraconal compartment (dermoid/epidermoid, lacrimal gland tumours, lymphoma, rhabdomysarcoma), and bone and sinus compartment (fibrous dysplasia). Lesions without any typical compartmental localization and those with multi-compartment involvement (veno-lymphatic malformation, plexiform neurofibroma, idiopathic orbital pseudotumour, IgG4 related disease, metastases) are also reviewed. We discuss the role of advanced imaging techniques, such as MR diffusion-weighted imaging (DWI), diffusion tensor imaging, fluoro-2-deoxy-D-glucose positron emission tomography CT (FDG-PET CT), and positron emission tomography MRI (MRI PET) as problem-solving tools in the evaluation of those orbital masses that present with non-specific morphologic imaging findings. Main messages/Teaching points • A compartment-based approach is essential for the diagnosis of orbital tumours. • CT and MRI play a key role in the work-up of orbital tumours. • DWI, PET CT, and MRI PET are complementary tools to solve diagnostic dilemmas. • Awareness of salient imaging pearls and diagnostic pitfalls avoids interpretation errors.

Bilateral persistent fetal vasculature due to a mutation in the Norrie disease protein gene

We report a case of a 7-week-old boy with bilateral leukocoria and asymmetric microphthalmia who was found to have Norrie disease. Symmetrically hyperdense globes with no evidence of calcification were seen on CT scan. The MRI showed bilateral retinal hemorrhages resulting in conical vitreous chambers-narrow at the optic disc and widened toward the lens-characteristic of persistent fetal vasculature. Genetic evaluation revealed a previously undescribed mutation in the Norrie disease protein gene.

Ophthalmic manifestations of systemic diseases--part 2: metabolic, infections, granulomatoses, demyelination, and skeletal dysplasias

The orbit and globe can be secondarily involved in various systemic diseases. These range from tumor and tumorlike conditions, metabolic, infective, inflammatory, granulomatous demyelinating diseases, and skeletal dysplasias. In this article, we discuss the imaging appearances of the remaining systemic pathologies affecting the orbit such as (1) endocrine or metabolic, (2) infectious, (3) inflammatory or granulomatous, (4) demyelinating diseases, and (5) skeletal dysplasias. As the imaging appearances of various systemic diseases tend to overlap, we also introduce a list of pattern-based systemic differential diagnoses for commonly encountered orbital imaging findings. Awareness of the imaging appearances of the various ophthalmic manifestations of systemic diseases can help a radiologist to suggest the most appropriate differential diagnosis to guide further workup and facilitate correct treatment.

Imaging of pediatric pathology during the Iraq and Afghanistan conflicts

United States Armed Forces radiologists deployed to Afghanistan and Iraq in modern military conflicts may encounter pediatric patients as a casualty of war or when providing humanitarian assistance to the indigenous population. Pediatric patients account for 4-7% of admissions at U.S. military hospitals during the Iraq and Afghanistan conflicts. It is pertinent for radiologists in the humanitarian care team to be familiar with imaging pediatric trauma patients, the pathology endemic to the local population, and delayed presentations of congenital and developmental disorders to adequately care for these patients. The radiological manifestations of various pediatric disorders seen in the setting of the Iraq and Afghanistan conflicts will be explored.

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.

Epidemiologic survey of infantile cancer in Iran based on the data of the largest pediatric cancer referral center (Ali- Asghar Children Hospital), 1996-2005

BACKGROUND

Cancer in infants younger than one year of age represents a unique problem with distinct epidemiological, clinical and genetic characteristics compared with older age groups. No report is yet available from Iran regarding epidemiological and survival rate of cancers diagnosed in this age group.

MATERIALS AND METHODS

The population under study comprised of patients which were diagnosed and admitted to Ali-Asghar hospital between years 1996-2005. In total, 287 infants were included in the retrospective descriptive survey. Patient files were evaluated for age of patient at the time of diagnosis, sex, geographical residence, consanguinity of parents, histological diagnosis, site of cancer involvement, type of therapy, date of last follow-up and cause of death (if applicable).

RESULTS

The average age at the time of diagnosis was 7.2 months old. The most frequent malignancy was retinoblastoma (44%), followed by leukemia (19%) and neuroblastoma (10%), with five-year overall survival rates of 77.7%, 41% and 90%, respectively Parents of 40 infants (13.9%) had consanguinity relationships.

CONCLUSIONS

Although we cannot make any conclusions regarding the incidence of infant cancer subtypes based on this study, survival rates for major types were similar to the developed countries, which signifies strict adherence to standards of care in Ali-Asghar hospital, the main infant cancer care centre in Iran. A Childhood Cancer Registry with high-resolution data collection and also advanced genetic testing is advocated for in-depth analysis of variation in incidence and survival.

Manifestations of pilocytic astrocytoma: a pictorial review

BACKGROUND

Pilocytic astrocytoma can be challenging to diagnose.

METHODS

Its clinical presentations can differ, directly related to its size and location, and are relatively unreliable. Similarly, imaging findings also vary with the location of the pilocytic astrocytoma.

RESULTS

This review provides an overview of the different imaging findings regarding pilocytic astrocytomas using both conventional and advanced magnetic resonance imaging sequences according to tumour location; the findings are strongly related to the tumour's tendency to infiltrate surrounding structures, being able to carry out gross total resection, and finally the prognosis.

CONCLUSIONS

Knowledge of these imaging manifestations of pilocytic astrocytoma may be helpful to arrive at an accurate diagnosis.

TEACHING POINTS

• To recognise the various imaging findings of pilocytic astrocytoma on both conventional and advanced magnetic resonance imaging sequences. • To identify the characteristic imaging findings according to tumour location. • To discuss the relevant differential diagnoses of pilocytic astrocytoma in each tumour location.

Case 206: persistent hypertrophic primary vitreous

History This patient was a 20-month-old full-term girl who had not received any routine pediatric care. During a physical examination, left-sided leukocoria was detected. Subsequently, a left-sided cataract was diagnosed. The patient was sent for magnetic resonance (MR) imaging of the brain and orbits.

Diffusion-weighted imaging of orbital masses: multi-institutional data support a 2-ADC threshold model to categorize lesions as benign, malignant, or indeterminate

BACKGROUND AND PURPOSE

DWI has been increasingly used to characterize orbital masses and provides quantitative information in the form of the ADC, but studies of DWI of orbital masses have shown a range of reported sensitivities, specificities, and optimal threshold ADC values for distinguishing benign from malignant lesions. Our goal was to determine the optimal use of DWI for imaging orbital masses through aggregation of data from multiple centers.

MATERIALS AND METHODS

Source data from 3 previous studies of orbital mass DWI were aggregated, and additional published data points were gathered. Receiver operating characteristic analysis was performed to determine the sensitivity, specificity, and optimal ADC thresholds for distinguishing benign from malignant masses.

RESULTS

There was no single ADC threshold that characterized orbital masses as benign or malignant with high sensitivity and specificity. An ADC of less than 0.93 × 10(-3) mm(2)/s was more than 90% specific for malignancy, and an ADC of less than 1.35 × 10(-3) mm(2)/s was more than 90% sensitive for malignancy. With these 2 thresholds, 33% of this cohort could be characterized as "likely malignant," 29% as "likely benign," and 38% as "indeterminate."

CONCLUSIONS

No single ADC threshold is highly sensitive and specific for characterizing orbital masses as benign or malignant. If we used 2 thresholds to divide these lesions into 3 categories, however, a majority of orbital masses can be characterized with >90% confidence.

A clinical update and radiologic review of pediatric orbital and ocular tumors

While pediatric orbital tumors are most often managed in tertiary care centers, clinicians should be aware of the signs of intraocular and orbital neoplasms. In the pediatric population, a delay in diagnosis of orbital and intraocular lesions, even if benign, can lead to vision loss and deformity. Intraocular lesions reviewed are retinoblastoma, medulloepithelioma, and retinal astrocytic hamartoma. Orbital neoplasms reviewed are rhabdomyosarcoma, neuroblastoma metastases, optic pathway glioma, plexiform neurofibroma, leukemia, lymphoprolipherative disease, orbital inflammatory syndrome, dermoid and epidermoid inclusion cysts, and Langerhans' cell histiocytosis. Vascular lesions reviewed are infantile hemangioma and venous lymphatic malformation. In conjunction with clinical examination, high-resolution ophthalmic imaging and radiologic imaging play an important role in making a diagnosis and differentiating between benign and likely malignant processes. The radiologic imaging characteristics of these lesions will be discussed to facilitate prompt diagnosis and treatment. The current treatment modalities and management of tumors will also be reviewed.

High-resolution MR imaging of the orbit in patients with retinoblastoma

Retinoblastoma is the most common intraocular childhood malignancy, with a prevalence of one in 18,000 children younger than 5 years old in the United States. In 80% of patients, retinoblastoma is diagnosed before the age of three, and in 95% of patients, retinoblastoma is diagnosed before the age of five. Although reports exist of retinoblastoma in adults, onset beyond 6 years of age is rare. Broadly, retinoblastoma may be classified into two groups: sporadic and heritable. In either case, the origin of the tumor is a biallelic mutation in primitive neuroepithelial cells. Although their details vary, several staging schemes are used to describe the extent of retinoblastoma according to the following four general criteria: intraocular location, extraocular (extraorbital) location, central nervous system disease, and systemic metastases. In the past decade, substantial changes have taken place in terms of staging and monitoring treatment in patients with retinoblastoma. Diagnosis and treatment of retinoblastoma involve a multidisciplinary approach, for which imaging is a vital component. Increasing awareness and concerns about the effects of radiation in patients with retinoblastoma have led to a shift away from external-beam radiation therapy and toward chemotherapy and locoregional treatment, as well as the establishment of magnetic resonance imaging as the most important imaging modality for diagnosis, staging, and treatment monitoring.

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.

Evaluation of orbital disorders and cranial nerve innervation of the extraocular muscles

A wide range of orbital disorders, including an orbital mass, infection, inflammation, systemic disease, or intracranial lesions, may be encountered with imaging. Evaluation of orbital disorders requires the combination of accurate and relevant clinical information with an understanding of anatomy and pathologic processes. An imaging approach to an orbital differential diagnosis includes assessment for alteration of a normal orbital structure, a lesion that does not belong in the orbit, or alteration of the orbit from bone or periorbital disorders. This approach, combined with key elements of clinical history, leads to a narrower differential diagnosis and improved patient care.

US and MRI of pediatric ocular masses with histopathological correlation

We review our experience with unusual ocular pathologies, some mimicking retinoblastoma, that were referred to our institution during the past two decades. After presenting the imaging anatomy of the normal eye, we discuss pertinent clinical and pathological features, and illustrate the US and MRI appearance of retinoblastoma, medulloepithelioma, uveal melanoma, persistent fetal vasculature, Coats disease, corneal dermoid, retinal dysplasia and toxocara granuloma. Features useful in discriminating among these entities are emphasized.

Abnormalities of the globe

Although much has been published in the radiology literature on the multitudinous conditions affecting the bony orbit, there has been relatively little on diseases confined to the globe itself. As current cross-sectional imaging techniques evolve, the globes can be visualized in ever greater detail, facilitating the recognition of even fairly subtle disease entities in this region. Indeed, the fact that high-resolution detailed images of this area are achievable without significant time or radiation penalty when evaluating surrounding structures means that incidental disease is not infrequently encountered. As such, common disease entities in this region are of interest to the general radiologist and the diagnosis of globe disease need not be the remit of experienced observers in specialist centres. At our institutions we have recently encountered a number of cases covering a broad spectrum of diagnoses including traumatic, neoplastic, iatrogenic, inflammatory, and infective aetiologies. The purpose of this review is to briefly revise the pertinent anatomical and physiological properties of the globe and to familiarize the reader with the computed tomography (CT) and magnetic resonance imaging (MRI) appearances of a number of these disease states. The collection of abnormalities included is not intended to be exhaustive, merely representative, with the emphasis towards those more commonly encountered.

Correlation of apparent diffusion coefficient at 3T with prognostic parameters of retinoblastoma

BACKGROUND AND PURPOSE

Pathologic prognostic parameters for retinoblastoma have been defined. Our purpose was to correlate ADC values at 3T with prognostic parameters of retinoblastoma.

MATERIALS AND METHODS

This study included 72 children (30 boys and 42 girls, mean age 19 ± 2.6 months) with retinoblastoma. Pretreatment diffusion-weighted MR imaging was performed on a 3T scanner with b factors of 0, 500, and 1000 seconds/mm(2). ADC values were calculated and pathologic specimens were analyzed. ADC values of the tumors were then correlated with prognostic parameters, including degree of histologic differentiation, tumor size, bilaterality, choroidal invasion, and optic nerve extension.

RESULTS

The mean ADC value of retinoblastoma was 0.49 ± 0.12 × 10(-3) mm(2)/s. The ADC values of well- and moderately differentiated tumors were significantly different (P = .007) from poorly and undifferentiated retinoblastoma. There was also a significant difference in the ADC value among small, medium, and large tumors (P = .015), as well as between unilateral and bilateral retinoblastoma (P = .001), and this was independent of the degree of differentiation. The ADC value was also significantly lower (P = .003) when optic nerve invasion was present. There was no correlation of ADC value with growth pattern or choroidal invasion (P = .640 and 0.661, respectively). The ADC value of retinoblastoma was well correlated with the degree of differentiation of the tumor (r = 0.87, P = .007) and inversely correlated with the size of the tumor (r = -0.68, P = .015).

CONCLUSIONS

ADC correlated with some of the accepted parameters of poor prognosis for retinoblastoma and may serve as a noninvasive prognostic parameter for assessment of newly diagnosed retinoblastoma.

Orbital lymphoma: imaging features and differential diagnosis

Purpose

Patterns of orbital lymphoma at diagnosis and follow-up are described. We also discuss differential diagnosis of orbital masses.

Materials and methods

This pictorial review contains 19 cases of orbital lymphoma before and after treatment. Superior-lateral quadrant and extra-conal location were observed predominantly. Effective response after treatment was presented on follow-up imaging, although few local relapses were found. Further follow-up showed no changes of residual images.

Discussion

Location of orbital masses can help in the differential diagnosis. Moreover, imaging features of lymphoma at diagnosis can be useful in planning surgical biopsy. Pattern of follow-up described may be relevant on monitoring imaging.

Teaching points

• Orbital lymphoma involves mainly superior-lateral quadrant and the orbital structures inside.

• Location of retrobulbar mass-like lesions are useful information in the differential diagnosis.

• Satisfactory response is detected after treatment, however relapse is noted, so follow-up is needed.

Leukocoria in a child with sturge-weber syndrome

A five-year-old girl with Sturge-Weber syndrome (SWS) presented with unilateral leukocoria. Imaging excluded retinoblastoma and revealed a choroidal hemangioma, a non-traumatic vitreous hemorrhage and a cataract. To the best of our knowledge, this is the first case report in the radiologic literature of these ophthalmologic findings presenting together and conditioning leukocoria in the setting of SWS. We discuss possible mechanisms and review the literature, emphasizing the role of neuroimaging in pediatric patients with SWS and ophthalmologic complaints.

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.

Diffusion-weighted imaging of malignant ocular masses: initial results and directions for further study

BACKGROUND AND PURPOSE

Ocular masses represent a spectrum of malignant tumors and benign lesions that are sometimes difficult to detect and differentiate by conventional imaging techniques. The aim of this study was to characterize a group of malignant ocular masses with DWI, with the goals of establishing reference data and identifying potential clinical applications for improved noninvasive characterization.

MATERIALS AND METHODS

With institutional review board approval, 26 malignant ocular masses in 22 patients were retrospectively analyzed. Five masses were excluded from further analysis due to nonvisualization. Fifteen retinoblastomas, 5 melanomas, and 1 highly undifferentiated carcinoma were studied. Region-of-interest analysis was performed, and the ADC of each mass was measured and also compared with a normal-appearing thalamus. Lesion thickness was measured, the amount of susceptibility artifact was qualitatively assessed and graded, and the correlation between these factors and retinoblastoma ADC was determined.

RESULTS

Retinoblastomas had an ADC of 0.93 ± 0.3 × 10(-3) mm(2)/s (mean). Melanoma had an ADC of 1.18 ± 0.16 × 10(-3) mm(2)/s. The ADC of retinoblastoma was strongly inversely correlated with lesion thickness, likely representing the effect of partial volume averaging. ADC was not correlated with the amount of subjectively determined susceptibility artifact.

CONCLUSIONS

Malignant ocular tumors were consistently characterized with DWI, though with limitations due to artifact and partial volume averaging. Additional description of DWI of ocular masses and further technical improvements may lead to a clinical role for DWI.

MRI of retinoblastoma

We review the role of MRI in retinoblastoma and simulating lesions. Retinoblastoma is the most common paediatric intra-ocular tumour. It may be endophytic, exophytic or a diffuse infiltrating tumour. MRI can detect intra-ocular, extra-ocular and intracranial extension of the tumour. MRI is essential for monitoring patients after treatment and detection of associated second malignancies. It helps to differentiating the tumour from simulating lesions with leukocoria.

The globe: infection, inflammation, and systemic disease

Infection, inflammation, and systemic diseases affecting the globe encompass a broad range of pathologies which may ultimately lead to progressive vision loss. Clinical symptomatology varies from the inexorably silent progressive visual loss to an acute presentation of ocular pain and/or red eye. Most are diagnosed by clinical ophthalmologic examination with selective use of ultrasound, computed tomography, and magnetic resonance imaging for confirmation of the diagnosis, assessment of disease extent, and signs of associated systemic disease. Knowledge of the differential diagnoses of vision loss, ocular pain, and redness makes imaging analysis of this diverse group of processes more precise.

Differentiation between benign and malignant orbital tumors at 3-T diffusion MR-imaging

INTRODUCTION

To differentiate between malignant and benign orbital tumors at 3-T diffusion MR imaging.

METHODS

A retrospective study was conducted on 47 patients (34 males and 13 females aged 4-74 years) with orbital masses. They underwent echo-planar diffusion-weighted MR imaging of the orbit with b-factor of 0, 500, and 1,000 s/mm(2) at 3-T MR unit. Apparent diffusion coefficient (ADC) maps were reconstructed, and the ADC value of the orbital mass was calculated.

RESULTS

The mean ADC value of the malignant orbital tumors (0.84 ± 0.34 × 10(-3) mm(2)/s) was significantly lower (P = 0.001) than that of the benign orbital tumors (1.57 ± 0.33 × 10(-3) mm(2)/s). The selection of an ADC value of 1.15 × 10(-3) mm(2)/s as a threshold value for differentiating malignant orbital tumors from benign lesions has a sensitivity of 95%, a specificity of 91%, and an accuracy of 93%. There was a significant difference in the ADC value between well- and poorly differentiated malignancies (P = 0.005).

CONCLUSION

Apparent diffusion coefficient value at 3 T is an additional noninvasive imaging parameter that can be used for the differentiation of malignant orbital tumors from benign lesions, the characterization of some orbital tumors, as well as the grading of orbital malignancy.

Malignant transformation of a medulloepithelioma of the optic nerve

OBJECTIVE

To describe a case of malignant transformation of a medulloepithelioma of the optic nerve.

METHODS

A 3-year-old boy presented with right-sided proptosis, swollen eyelids, restricted ocular movements, pain and nausea. Visual acuity was hand motions. A benign non-teratoid medulloepithelioma of the optic nerve was surgically removed. Due to relapse in the orbit 10 months postoperatively enucleation and partial orbital exenteration were performed. Light microscopy and immunohistochemistry now revealed a malignant medulloepithelioma. The boy was further treated with chemotherapy and radiotherapy and is still alive 36 months after primary surgery.

RESULTS

Medulloepithelioma of the optic nerve is extremely rare. Only eight cases have been described in the literature. Unlike intraocular medulloepithelioma, all have been malignant tumours. This is the first case described of a benign medulloepithelioma of the optic nerve, later transforming into a malignant tumour. One third of patients with medulloepithelioma of the optic nerve have died from direct intracranial spread or metastasis to the central nervous system (CNS).

CONCLUSIONS

Medulloepithelioma of the optic nerve should be considered malignant despite morphology with tendency to spread to the CNS. Furthermore; it should be considered as a differential diagnosis when observing a tumour of the optic nerve in a child.