Figure 19-1 Genetic counseling for retinoblastoma. (Chart created by David H. Abramson, MD.)
Diagnostic Evaluation
Retinoblastoma is a clinical diagnosis. Fine-needle aspiration biopsy (FNAB) should be undertaken only with extreme caution and only by an experienced ocular oncologist, because of the risk of systemic dissemination of tumor.
Clinical Examination
The presenting signs and symptoms of retinoblastoma are determined by the extent and location of tumor at the time of diagnosis. In the United States, the most common presenting signs of retinoblastoma are leukocoria (white pupillary reflex), strabismus, and ocular inflammation (Table 19-2; Fig 19-2). Other presenting features, such as iris heterochromia, spontaneous hyphema, and orbital cellulitis or inflammation are uncommon. In rare instances, a small lesion may be found on routine examination. Visual complaints are infrequent because most patients are preschool-aged children.
The diagnosis of retinoblastoma can generally be suspected on the basis of an office examination with documented visual acuity. An examination under anesthesia (EUA) is needed in all patients suspected of having retinoblastoma to permit a complete assessment of the extent of ocular disease prior to treatment (Fig 19-3). The intraocular pressure and corneal diameter of both eyes should be measured intraoperatively. The location of all tumors in each eye should be clearly documented. Retinoblastoma begins as a translucent, gray to white intraretinal tumor, fed and drained by dilated, tortuous retinal vessels (Fig 19-4). As the tumor grows, foci of calcification develop, giving the characteristic chalky white appearance. Exophytic tumors grow beneath the retina and may have an associated serous retinal detachment (Fig 19-5). As the tumor grows, the retinal detachment may become extensive, obscuring visualization of the tumor (Fig 19-6). Endophytic tumors grow on the retinal surface into the vitreous cavity. Blood vessels may be difficult to discern in endophytic tumors. Endophytic tumors are more apt to give rise to vitreous seeds (Fig 19-7). Cells shed from retinoblastoma remain viable in the vitreous and subretinal space and may eventually give rise to tumor implants throughout the eye. Vitreous seeds may also enter the anterior chamber, where they can aggregate on the iris to form nodules or settle inferiorly to form a pseudohypopyon (Fig 19-8). Secondary glaucoma and rubeosis iridis occur in approximately 50% of such cases. A rare variant of retinoblastoma is the diffuse infiltrating retinoblastoma, which is detected at a later age (>5 years) and is typically unilateral. Diffuse infiltrating retinoblastoma presents a diagnostic dilemma, as the retina may be difficult to see through the dense vitreous cells. This variant is often mistaken for an intermediate uveitis of unknown etiology.
Table 19-2
Figure 19-2 Retinoblastoma. A, Clinical appearance shows leukocoria and strabismus associated with advanced intraocular tumor. B, High magnification. Note large retrolental tumor and secondary total exudative retinal detachment. (Courtesy of Timothy
G. Murray, MD.)
Figure 19-3 Retinoblastoma. Multiple tumor foci in an eye of a patient with a germline RB1 mutation. (Courtesy of Matthew W.
Wilson, MD.)
Figure 19-4 Retinoblastoma, clinical appearance. Small, discrete white tumor supplied by dilated retinal blood vessels.
(Courtesy of Timothy G. Murray, MD.)
Figure 19-5 Retinoblastoma. Note the dilated retinal blood vessels, foci of calcification (arrow), and cuff of subretinal fluid
(asterisk). (Courtesy of Matthew W. Wilson, MD.)
Figure 19-6 Retinoblastoma. Complete exudative detachment obscures tumor visualization. Note normal-appearing retinal vessels as opposed to those found in Coats disease. (Courtesy of Matthew W. Wilson, MD.)
Ultrasonography can be helpful in the diagnosis of retinoblastoma by demonstrating characteristic calcifications within the tumor. Although these calcifications can also be seen on CT scan, MRI has become the preferred diagnostic modality for evaluating the optic nerve, orbits, and brain. MRI not only offers better soft-tissue resolution, but also avoids potentially harmful radiation exposure. Recent studies have suggested that systemic metastatic evaluation, typically bone marrow and lumbar puncture, is not indicated in children without neurologic abnormalities or evidence of extraocular extension. If optic nerve extension is suspected, lumbar puncture may be performed. Parents and siblings should be examined for evidence of untreated retinoblastoma or retinocytoma, as this would provide evidence for a hereditary predisposition to the disease. Children with retinoblastoma should have a complete history and physical examination by a pediatric oncologist.
Figure 19-7 Retinoblastoma. Large endophytic tumor with extensive vitreous seeding (arrows). (Courtesy of Matthew W. Wilson,
MD.)