Chapter 154 – Astrocytoma of Retina
JAMES J. AUGSBURGER
ALAN F. CRUESS
• Benign neuroglial tumor that arises from retinal astrocytes.
• Translucent to opaque white inner retinal tumor.
• Tuberous sclerosis in many affected individuals, especially those who have bilateral, multifocal retinal lesions.
The retinal astrocytoma is a benign acquired neoplasm that arises from astrocytes of the sensory retina. Lesions of this type occur in a multifocal bilateral pattern that is frequently associated with tuberous sclerosis and in a unilateral, unifocal pattern that usually represents a sporadic nonsyndromic disorder.
EPIDEMIOLOGY AND PATHOGENESIS
Astrocytoma of the retina appears to be rare, but its precise frequency in the general population has not been determined. The tumor tends to arise early in life and is frequently detected during childhood or adolescence. However, some lesions are not noted until adulthood. Astrocytoma of the retina affects all ethnic groups and both sexes equally. Recognized risk factors for development of an astrocytoma of the retina include tuberous sclerosis and possibly neurofibromatosis (see Systemic Associations ).
Patients who have one or more retinal astrocytomas usually have no visual symptoms unless the tumor involves the macula. Occasionally, a retinal astrocytoma remote from the fovea causes a nonrhegmatogenous retinal detachment that involves the macular retina and abruptly blurs the vision in that eye.
The retinal astrocytoma usually appears as a white, superficial retinal mass.  The clinical spectrum of retinal astrocytomas
Figure 154-1 Small translucent retinal astrocytoma. The patient was an 11-year-old boy who had tuberous sclerosis.
characteristically ranges from faint translucent intraretinal patches ( Fig. 154-1 ) through more distinctly nodular, opaque white, inner-retinal lesions to dense partially calcified mulberry-like tumors ( Fig. 154-2 ). Lesions of these three types may be present simultaneously in the same eye. The lesion is vascularized from the retina, but its afferent and efferent blood vessels are usually not particularly dilated or tortuous. Retinal astrocytomas can arise from any location in the retina, from the optic disc and macula to the oral zone. Patients who have tuberous sclerosis or neurofibromatosis and develop retinal astrocytomas are more likely to have multiple and more peripheral lesions than patients with the nonsyndromic disease.
An atypical type of retinal astrocytoma is the isolated nonsyndromic lesion that occurs unilaterally in otherwise unaffected individuals ( Fig. 154-3 ). Lesions of this type can attain a relatively large size and cause profound visual loss, usually on the basis of their macular location or accumulation of exudative subretinal fluid. Unless the possibility of an astrocytoma is considered clinically, eyes that have this sort of tumor usually come to enucleation because amelanotic choroidal melanoma or another malignant neoplasm is suspected.
DIAGNOSIS AND ANCILLARY TESTING
In most cases, conventional diagnostic testing does not help in diagnosis or treatment planning. Fluorescein angiography of a classical retinal astrocytoma typically shows relatively slow filling of the intralesional vasculature, absence of dilated afferent
Figure 154-2 Calcified mulberry-like retinal astrocytoma partially overlying optic disc. The patient had tuberous sclerosis.
Figure 154-3 Isolated nonsyndromic retinal astrocytoma with secondary retinal detachment. The patient was a 35-year-old woman.
Figure 154-4 Fluorescein angiography of retinal astrocytoma. A, Retinal venous phase frame showing multitude of fluorescent small blood vessels within generally hypofluorescent mass. B, Late phase frame showing diffuse staining of astrocytoma and associated serous subretinal fluid.
Differential Diagnosis of Retinal Astrocytoma
• Toxocara granuloma
• Exaggerated macular exudative lesion in idiopathic retinal telangiectasis or retinal capillary hemangiomatosis
• Isolated patch of myelinated retinal nerve fibers
• Amelanotic choroidal melanoma
• Massive gliosis of retina
and efferent retinal vascular channels, and limited late staining of the tumor ( Fig. 154-4 ). Isolated retinal astrocytomas characteristically exhibit prominent surface vascularity, which helps differentiate these lesions from amelanotic choroidal melanomas that have retinal invasion. B-scan ultrasonography shows small noncalcified retinal astrocytomas to be ill-defined lesions having reflectivity similar to that of normal retina. In contrast, B scan shows larger calcified retinal astrocytomas to have focal strong intralesional reflections and orbital shadowing by the mass. Computed tomography and magnetic resonance imaging can reveal characteristic central nervous system lesions of tuberous sclerosis but are not otherwise particularly helpful in the differential diagnosis. Occasionally, fine-needle aspiration biopsy can help to establish the diagnosis of an atypical retinal astrocytoma.
The lesions and disorders that should be considered in the differential diagnosis of retinal astrocytoma are listed in Box 154-1 .
Treatment Options for Retinal Astrocytomas
• Observation (most cases)
• Enucleation (blind painful eyes due to intraocular progression of tumor)
As indicated previously, multifocal bilateral retinal astrocytomas usually occur in the context of tuberous sclerosis.  In contrast, most unilateral unifocal retinal astrocytomas occur as isolated lesions in patients who have no underlying systemic disorder.
Baseline Systemic Evaluation
Because of the benign nature of the retinal astrocytoma, a baseline systemic evaluation for malignancy is not warranted. However, an assessment aimed at the detection of other features of tuberous sclerosis or neurofibromatosis is appropriate.
The typical retinal astrocytoma consists of a mass of interlacing spindle-shaped fibrous astrocytes that contain small bland elongated oval nuclei and have indistinct wavy cytoplasmic borders. Larger lesions frequently contain foci of calcification. Many retinal astrocytomas, especially those that occur in tuberous sclerosis or neurofibromatosis, also contain plump, polygonal cells having eosinophilic cytoplasm that have been termed giant astrocytes. The retinal astrocytoma is regarded by many ophthalmic pathologists as a hamartoma (a benign congenital tumor composed of tissue elements that are normal for the location in which they occur) rather than as an acquired neoplasm.
For most retinal astrocytomas, no treatment is required ( Box 154-2 ). For patients whose intraocular tumor enlarges progressively and eventuates in a blind, painful eye, enucleation seems to be the only effective treatment. Radiotherapy by plaque or charged particle beam has not been shown to be effective.
COURSE AND OUTCOMES
Astrocytomas of the retina tend to develop early in childhood and show some tendency for limited progression during the childhood years. However, these tumors have extremely limited malignant potential and do not metastasize. If they occur in or adjacent to the foveola, they can cause visual loss on the basis of progressive retinal degeneration. In most cases, however, they are associated with normal visual acuity.
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