|Year : 2006 | Volume
| Issue : 4 | Page : 657-668
|Pictorial essay: USG of retinoblastoma
HC Soni, SB Patel, KG Goswami, Y Gohil
Department of Radio-diagnosis, Gujarat Cancer and Research Institute, Asarwa, Ahmedabad - 380016, India
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|Date of Submission||15-Sep-2006|
|Date of Acceptance||10-Nov-2006|
Keywords: Retinoblastoma, USG, CT Scan
|How to cite this article:|
Soni H C, Patel S B, Goswami K G, Gohil Y. Pictorial essay: USG of retinoblastoma. Indian J Radiol Imaging 2006;16:657-68
|How to cite this URL:|
Soni H C, Patel S B, Goswami K G, Gohil Y. Pictorial essay: USG of retinoblastoma. Indian J Radiol Imaging [serial online] 2006 [cited 2021 Feb 25];16:657-68. Available from: https://www.ijri.org/text.asp?2006/16/4/657/32294
| Introduction|| |
Retinoblastoma is the most common primary ocular malignancy of childhood. It is highly malignant tumor. Peter Pawius of Amsterdam made the first description of a tumor resembling retinoblastoma. In 1836, Langenbech, Robin, and Nystin of Paris confirmed by microscopic studies that the tumor definitely arose from the retina. In 1970, Tso and colleagues established that the tumor arises from photoreceptor precursors . Commonly used estimate is 1 case of retinoblastoma per 18,000-30,000 live births, depending on the country. In developed countries retinoblastoma are early detected while in developing and underdeveloped countries, retinoblastoma is often detected after is has invaded the orbit or brain.
| Discussion|| |
Leucocoria is the most common presenting sign, accounting for about 56.1% of cases. Retinoblastoma can cause secondary changes in the eye, including glaucoma, strabismus, retinal detachment, and inflammation secondary to tumor necrosis. Proptosis is a more common presenting symptom in most underdeveloped countries.
Most retinoblastoma continues to be quite advanced at the time of diagnosis and enucleation or external beam radiotherapy [EBRT] will remain the only therapeutic options in such cases. Newer modalities of treatment like laser ablation, photocoagulation, cryotherapy have been introduced. Early results of new treatment modalities suggest that retinoblastoma, if diagnosed early enough can be managed without enucleation or any form of irradiation. Thus, the importance of early diagnosis becomes obvious. It is apparent that if all retinoblastoma could be recognized either in utero or shortly after birth, most of them could be treated promptly by the aforementioned methods, thus saving the child's life and salvaging useful vision . One such case report had been made where retinoblastoma is diagnosed by High-resolution sonography [HRSG] in newborn who had family history of retinoblastoma. On HRSG membrane like lesion seen in eye with hyper-reflective peak on A mode. Tumor was successfully treated by photocoagulation . It is recommended that routine clinical screening of all parents and sibling of retinoblastoma patient to provide earlier detection of retinoblastoma and treatment at presymptomatic disease stage .
High-resolution sonography (HRSG) has firmly established itself as prime imaging modality for superficial parts and small parts scanning. Excellent tissue details with anatomical landmarks are the hallmark of the technique. The prerequisite for HRSG is high frequency transducers ranging from 5 MHz to 15 MHz with short focus. The biggest advantage of HRSG is that it is noninvasive, cost effective and rapid investigation. No specific preparation or sedation is required. Echography is very useful for the detection and differentiation of intraocular tumor in children and is particular valuable in diagnosis of Retinoblastoma . We have had performed USG of orbit on SIEMEN G50 machine using 7.5-10 MHz linear probe.
Intraocularly Retinoblastoma exhibits three pattern of tumor growth,
| Endophytic growth|| |
Endophytic growth occurs when the tumor breaks through the internal limiting membrane. Small Retinoblastoma are smooth, dome shaped and shows homogenous hypoechoic echopattern [Figure - 1] however, large tumors are highly irregular and heterogeneous in texture. Usually it comes out from on site of retina and fills the posterior segment [Figure - 2],[Figure - 3]. But in rare case tumor involving all the surface of retina can be found on HRSG known as retinoblastoma circumference. Calcification is typical feature of retinoblastoma and is accompanied with acoustic shadowing. The presence of intraocular calcium in children under three years of age is highly suggestive of retinoblastoma. Rarely calcification is absent [Figure - 4]. Effected eye may show normal or higher then normal axial length. Retinoblastoma in microophthalmic eye is extremely rare. HRSG can also tell about the extra ocular extension of the tumor. The eye is usually of normal size or is larger then normal . Retinoblastoma may be unilateral or bilateral [Figure - 5], focal or multifocal [Figure - 6],[Figure - 7].
Endophytic tumor growth pattern can be associated with vitreous seeding wherein small fragments of tissue become separated from the main tumor. In some instances, vitreous seeding may be extensive allowing tumor cells to be visible as spheroid masses floating in the vitreous and anterior chamber. Secondary deposits or seeding of tumor cells into other areas of the retina may be confused with multicentric tumors. Differentiation between multifocal lesion and tumor seedling may be difficult . Vitreous seedling produces vitreous echogenic debris on HRSG. Vitreous echogenic debris may also results from hemorrhage or increased globulin content. Most tumors exhibit both exophytic and endophytic growth.
Retinoblastoma can extend to involve anterior chamber. On HRSG few solid and cystic nodules can be seen. Tumor can be discovered posterior to iris, on the lens capsule and over ciliary process. Other HRSG findings include angle closure related to iris, neovascularization and uveal thickening .
Retinoblastoma can lead to metastasis at different site. Cases had been reported with liver [Figure - 8], ovary , skin  and bone metastasis. The vascularity indicates tumor activity; that is, lesions are hypervascular at diagnosis and when active. Vascularity regresses with treatment . Echography is also useful in monitoring size of tumor and complication in post chemotherapy or radiotherapy status. In most instances, tumors that recur or continue to grow after radiotherapy tend to exhibit low to medium reflectivity and do not show calcification. Tumor tends to outgrow their blood supply resulting in areas of necrosis ,.
CT detects intraocular, extraocular, and intracranial disease extension; excels at delineation of bony abnormalities; and readily depicts tumoral calcifications. Delineation of intraocular soft-tissue detail is limited with CT. Contrast enhancement is typically used but may obscure underlying calcifications unless preceded by a nonenhanced study.
On CT, retinoblastoma is characterized by enhancing intermediate-density soft-tissue mass or masses, with varying degrees of calcification; calcification increases with therapeutic response. The vitreous may be abnormally dense from debris, hemorrhage, or increased globulin content. Differentiation between noncalcified tumor and hemorrhage may be difficult. Retinoblastoma usually larger in size at presentation, and due to dense acoustic shadowing of calcium, detection of optic nerve involvement or extraocular extension of lesion may become difficult. In such cases CT scan would of help [Figure - 9].
Prognosis can be predicted from extent of lesion at presentation. Response of tumor after chemotherapy alone can be predicted from certain criteria. Large size retinoblastoma and retinoblastoma located at macular region responses more to chemotherapy. While lesion less then 2mm. size and in patient less then 2months of age responses less to chemotherapy .
Survival rates decrease to 60% if the tumor extends beyond the lamina cribrosa even if the cut end of the nerve is free of tumor cells. Survival rates decrease to less than 20% if the tumor cells are found at the surgical transaction sight. Intracranial extension can lead to death .
Retinoblastoma is rare but extremely important disease since its misdiagnosis is one of the few errors in the practice that can lead to death of a child.
Exophytic growth occurs in the subretinal space. This growth pattern often is associated with subretinal fluid accumulation and retinal detachment [Figure - 8]. The tumor cells may infiltrate through the Bruch membrane into the choroid and then invade either blood vessels or ciliary nerves or vessels. Tumor may grow outside eyeball. Typically retinoblastoma growing outside eyeball does not show presence of calcification [Figure - 10].
Diffuse infiltrating growth
This is a rare subtype comprising 1.5% of all retinoblastoma. It is characterized by a relatively flat infiltration of the retina by tumor cells but without a discrete tumor mass. It grows slowly compared with typical retinoblastoma. It typically lakes calcification, is seen in older patient and readily stimulate inflammatory or haemorrhagic process ,.
Reese and Ellsworth have developed a generally adopted classification system for intraocular retinoblastoma that has been shown to have prognostic significance.
Group I: very favorable for maintenance of sight
1. Solitary tumor, smaller than 4 disc diameters, at or behind the equator.
2. Multiple tumors, none larger than 4 disc diameters all at or behind the equator.
Group II: favorable for maintenance of sight
1. Solitary tumor, 4-10 disc diameters at or behind the equator.
2. Multiple tumors, 4-10 disc diameters behind the equator.
Group III: possible for maintenance of sight
1. Any lesion anterior to the equator.
2. Solitary tumor, larger than 10 disc diameters behind the equator.
Group IV: unfavorable for maintenance of sight
1. Multiple tumors, some larger than 10 disc diameters.
2. Any lesion extending anteriorly to the ora serrata.
Group V: very unfavorable for maintenance of sight
1. Massive tumors involving more than one half the retina.
2. Vitreous seeding.
Retinocytomas are rare tumors that are composed entirely of benign-appearing cells. Genetic implications of retinocytoma are the same as that of retinoblastoma. Family members of patients with retinoblastoma should be closely examined for retinocytoma and if positive, follow up periodically throughout their lives .
Trilateral retinoblastomas are cases of bilateral retinoblastoma associated with an ectopic intracranial retinoblastoma usually involving the pineal gland or the parasellar region. Trilateral retinoblastomas contribute significantly to the overall mortality in patients with hereditary retinoblastoma in the first decade of life accounting for approximately 50% of deaths. Screening efforts for patients with trilateral retinoblastoma should be directed to those at risk namely those patients with bilateral or multifocal disease and those with a positive family history. Patients and their siblings should be assessed periodically for any signs of developing.
Standard therapy comprises enucleation for unilateral disease and radiation therapy with or without enucleation for bilateral disease. However, contemporary treatment for retinoblastoma is transitioning to front-line chemotherapy to improve disease control while preserving vision and minimizing adverse sequel of enucleation and radiation therapy. Retinoblastoma contracts, calcifies, and becomes hypovascular in response to therapy . Long term follow up is essential for managing retinoblastoma after eye preserving conservative therapy .
Imaging of retinoblastoma after treatment is major concern. Post conservative treatment, the size of tumor decreases, with ultimately calcified spot, fibrosis remains as residue of previous treatment [Figure - 11]. In post enucleation status, USG is very sensitive modality to detect residual/recurrent mass in the same side [Figure 12] or development of tumor in opposite eye [Figure 13],[Figure 14].
EBRT can lead to various complications. Radiation can lead to cataract formation in 18 months to 3+ years. Retinal vascular damage and hemorrhage may be seen after external beam radiation or post chemotherapy [Figure 15]. Hypoplasia of bone and soft tissue structures after treatment with radiation doses exceeding 3500 cGy may occur. The maxillary molar tooth buds located high in the maxilla just inferior to the posterior apex of the orbit may become irradiated with treatment. Numerous reports of failure of tooth eruption have been noted in patients with retinoblastoma treated with irradiation.
Secondary nonocular tumors can develop in survivors of retinoblastoma, in order of decreasing frequency: osteosarcoma , [Figure 16],[Figure 17], various soft tissue sarcomas, malignant melanoma, various carcinomas, leukemia and lymphoma, and various brain tumors . Patients treated with EBRT appear to be at a much greater risk of developing second tumors. Dunkel et al demonstrated that by age 40 years 6% of those patients who did not receive EBRT had developed second primary malignant neoplasms as compared to 35% for those who did receive EBRT.
Differential diagnosis of retinoblastoma includes PHPV, retinopathy of prematurity, coat's disease, retinal astrocytoma, toxocariasis and optic nerve head drusen.
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H C Soni
Department of Radio-diagnosis, Gujarat Cancer & Research Institute, Asarwa, Ahmedabad - 380016
Source of Support: None, Conflict of Interest: None
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11]
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