Figure 19-8 Retinoblastoma, clinical appearance. Pseudohypopyon resulting from migration of tumor cells into the anterior chamber (masquerade syndrome).
In the United States, patients rarely present with metastases or intracranial extension at the time of diagnosis. The most frequently identified sites of metastatic involvement in children with retinoblastoma include skull bones, distal bones, brain, spinal cord, lymph nodes, and abdominal viscera. Retinoblastoma cells may escape the eye by invading the optic nerve and extending into the subarachnoid space. In addition, tumor cells may massively invade the choroid before traversing emissary canals or eroding through the sclera to enter the orbit. Extraocular extension may result in proptosis as the tumor grows in the orbit (Fig 19-9). In the anterior chamber, tumor cells may invade the trabecular meshwork, gaining access to the conjunctival lymphatics. The patient may subsequently develop palpable preauricular and cervical lymph nodes.
Differential Diagnosis
A number of lesions simulate retinoblastoma (Table 19-3). Most of these conditions can be differentiated from retinoblastoma on the basis of a comprehensive history, clinical examination, and appropriate ancillary diagnostic testing.
Persistent fetal vasculature
Persistent fetal vasculature (PFV), previously known as persistent hyperplastic primary vitreous (PHPV), is typically recognized within days or weeks of birth. The condition is unilateral in twothirds of cases and is associated with microphthalmos, a shallow or flat anterior chamber, a
hypoplastic iris with prominent vessels, and a retrolenticular fibrovascular mass that draws the ciliary body processes inward. On indirect ophthalmoscopy, a vascular stalk may be seen arising from the optic nerve head and attaching to the posterior lens capsule. Ultrasonography confirms the diagnosis by showing persistent hyaloid remnants arising from the optic nerve head, usually in association with a closed funnel retinal detachment. No retinal tumor is seen, and the axial length of the eye is shortened. Calcification may be present. PFV may be managed with combined lensectomy and vitrectomy approaches in selected cases. See also Chapter 10 in this volume and BCSC Section 6,
Pediatric Ophthalmology and Strabismus.
Figure 19-9 Retinoblastoma, clinical appearance. Proptosis caused by retinoblastoma with orbital invasion.
Table 19-3
Coats disease
Coats disease is clinically evident within the first decade of life and is more common in boys. The lesion is typically characterized by unilateral retinal telangiectasia associated with intraretinal yellow
exudation without a distinct mass (Fig 19-10). The progressive leakage of fluid may lead to an extensive retinal detachment and neovascular glaucoma. Ultrasonography documents the absence of a retinal tumor and shows the convection of cholesterol in the subretinal fluid. Fluorescein angiography shows classic telangiectatic vessels. Laser photocoagulation or cryoablation of the vascular anomalies eliminates the exudative component of the disease and may restore visual function. Subretinal fluid may be drained to facilitate these procedures. Serial evaluation and followup is critical for these patients.
Ocular toxocariasis
Ocular toxocariasis typically occurs in older children with a history of soil ingestion or exposure to puppies. Toxocariasis presents with posterior and peripheral granulomas, with an associated uveitis. Exudative retinal detachment, organized vitreoretinal traction, and cataracts may be present. Ultrasonography shows the vitritis, retinal detachment, granulomas, retinal traction, and the absence of calcium. See BCSC Section 9, Intraocular Inflammation and Uveitis, for additional discussion.
Astrocytoma
Retinal astrocytoma, or astrocytic hamartoma, generally appears as a small, smooth, white, glistening tumor located in the nerve fiber layer of the retina (Fig 19-11). It may be single or multiple, unilateral or bilateral. In some cases, it may become larger and calcified, typically having a mulberry appearance. Astrocytomas occasionally arise from the optic disc; such tumors are often referred to as giant drusen. Astrocytomas of the retina commonly occur in patients with tuberous sclerosis and may also be seen in patients with neurofibromatosis. Most retinal astrocytomas are not associated with a phakomatosis.
Figure 19-10 Coats disease. A, Clinical appearance of characteristic lightbulb aneurysms (arrowheads) observed in Coats disease. Note the associated exudative retinal detachment with subretinal exudate (asterisk). B, Fluorescein angiogram showing classic telangiectatic vessels (arrowhead). C, B-scan in Coats disease shows retinal detachment (arrows). D, In contrast, B-scan in retinoblastoma shows total retinal detachment (arrowhead) and a large tumor mass (asterisk). (Parts A and
B courtesy of Matthew W. Wilson, MD.)
Figure 19-11 Retinal astrocytic hamartomas, clinical appearance. Note the more subtle opalescent lesion (between arrows) superonasal to the optic disc and the larger “mulberry” lesion inferonasal to the disc.