Bilateral Retinoblastoma Joseph Junewick, MD FACR 06/11/2010 History 17 month old adopted female with proptosis. Diagnosis Bilateral Retinoblastoma Discussion Retinoblastoma is the most common pediatric intraocular neoplasm. It is a highly malignant tumor of the primitive neural retina. Modern cure rates are greater than 90%; extraocular extension occurs in less than 10% of patients and is associated with a considerably higher mortality rate. Retinoblastoma spreads by direct extension into the orbit along scleral emissary vessels, invasion of the optic nerve, and dispersion through the cerebrospinal fluid. The growth pattern of retinoblastoma can be subdivided into three types: endophytic, exophytic, and combined endophytic and exophytic. Endophytic tumors arise from inner layers of the retina and grow into the vitreous. Exophytic tumors start in the outer layers and growth is in the subretinal space. Beside enucleation, conservative treatment methods, such as thermochemotherapy, radioactive plaque therapy, cryotherapy, laser photocoagulation, external-beam radiation therapy, and tumor reduction chemotherapy, can be applied. The treatment of retinoblastoma depends on several parameters: tumor volume and localization, intraocular tumor extension, extraocular stage of disease, and laterality (side) of tumor. Magnetic resonance imaging is preferred for staging and should include intraocular (choroid, sclera, prelaminar optic nerve), extraocular (postlaminar optic nerve or orbital invasion) and intracranial (pineal and leptomeningeal metastases) evaluation for tumor spread. The reported predictors for metastatic retinoblastoma are invasion of the optic nerve, invasion of the choroid, and orbital involvement. Anterior chamber involvement is associated with an increased risk for metastases. Optic nerve invasion is reported to be present more often in patients with exophytic retinoblastoma, tumor thickness of 15 mm or larger, and vitreous hemorrhage. CT should not be routinely performed in hereditary retinoblastoma since cumulative radiation effects increases the risk for the development of second primary tumors. Findings MR-Axial and coronal T1, fat-suppressed T2 and fat-suppressed postgadolinium T1 images reveal bilateral intraocular masses. Intraorbital extension on the right is predominantly retrobulbar resulting in proptosis. The right oculus is small and associated with retinal detachment. Reference degraaf P, Barkoff F, Moll AC, Imhof SM, Knol DL, van der Valk P, Castelijns JA. Retinoblastoma: MR imaging parameters in detection of tumor extent. Radiology (2005); 235:197-207.
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