Chapter 156 – Combined Hamartoma of Retina
JAMES J. AUGSBURGER
SANFORD M. MEYERS
• Benign congenital tumor composed of retinal pigment epithelium, retinal astrocytes, and retinal blood vessels.
• Gray, deep retinal mass that has superficial gliotic component and tortuous intralesional blood vessels.
• Juxtapapillary tumor location.
• Other features of neurofibromatosis type 2 in substantial proportion of cases.
The combined hamartoma of the retina is an unusual benign congenital retinal tumor composed of sensory retina, retinal pigment epithelium, retinal blood vessels, and vitreoretinal membranes. It tends to be unilateral and unifocal in most cases. It characteristically involves the juxtapapillary retina, macula, or both and frequently causes moderate to profound visual impairment in the affected eye. Fortunately, the combined hamartoma of the retina has no recognized malignant potential.
EPIDEMIOLOGY AND PATHOGENESIS
The combined hamartoma is an uncommon lesion, but its precise frequency in the general population is unknown. It is presumably congenital, but most cases have not been detected before the age of 6 years. It appears to affect men and women equally, and it has been reported to occur in various racial groups. The only currently recognized risk factor for development of combined hamartoma of the retina appears to be the presence of neurofibromatosis (usually type 2; see Systemic Associations ).
The most common presenting feature is painless loss of vision or amblyopia in the involved eye caused by macular involvement. Other presenting symptoms include strabismus, floaters, and leukokoria. Patients who have an extramacular lesion of this type generally have no symptoms related to the mass.
The typical combined hamartoma of the retina is characterized by a whitish superficial appearance caused by epiretinal and intraretinal gliosis, marked tortuosity of the involved retinal arterioles and venules, and deep grayish-black pigmentation ( Fig. 156-1 ). The lesion is usually located in a juxtapapillary or circumpapillary position. It frequently achieves a size of 4–6?mm in diameter, but smaller and larger lesions have been encountered. Combined hamartomas of the retina occur occasionally in extrapapillary and peripheral fundus locations ( Fig. 156-2 ).
Figure 156-1 Typical combined hamartoma of retina. Note typical juxtapapillary and epipapillary location of lesion. The patient was a child who was subsequently found to have bilateral acoustic neuromas and other features of neurofibromatosis type 2.
Figure 156-2 Atypical combined hamartoma of retina. Lesion is located in inferotemporal periphery of right eye.
DIAGNOSIS AND ANCILLARY TESTING
Fluorescein angiography in the typical case reveals relative hypofluorescence of the lesion caused by the intrinsic retinal pigment epithelial pigmentation in the early phase frames. The prominent intralesional blood vessels fluoresce brightly in the arterial and venous phase frames and accentuate the ophthalmoscopically evident intralesional vascular tortuosity. By the late phase of the study, the lesion often appears diffusely hyperfluorescent because of fluorescein leakage from the abnormal intralesional blood vessels.
B-scan ultrasonography can image thicker lesions but is not particularly helpful in differential diagnosis. Computed tomography and magnetic resonance imaging can reveal bilateral acoustic neuromas (the characteristic feature of neurofibromatosis type 2) in patients who have that syndromic association (see Systemic Associations ).
The several lesions that should be considered in the differential diagnosis of combined hamartoma of the retina are listed in Box 156-1 .
Differential Diagnosis of Combined Hamartoma of the Retina
• Choroidal melanoma (if intrinsic melanotic pigmentation is prominent)
• Retinoblastoma (if superficial white gliosis is prominent)
• Capillary hemangioma of retina (if vascular component is prominent)
• Idiopathic or postinflammatory surface wrinkling retinopathy
• Reactive hyperplasia of retinal pigment epithelium
• Massive gliosis of retina
Although most cases of combined hamartoma of the retina appear to be sporadic and nonsyndromic, a considerable number of individuals with such a lesion have been found to have neurofibromatosis type 2 (central neurofibromatosis).    A weaker but still noteworthy association with neurofibromatosis type 1 has also been reported by some authors. Because of these associations, all patients who have a combined hamartoma of the retina should be evaluated for the presence of other clinical manifestations of neurofibromatosis types 1 and 2.
Baseline Systemic Evaluation
Because this lesion has no recognized malignant potential, baseline systemic evaluation to look for extraophthalmic malignancies is not warranted. However, newly diagnosed children should be evaluated for neurofibromatosis, especially neurofibromatosis type 2.
The few pathological specimens that have been reviewed and reported have been composed of interlacing cords of hyperplastic retinal pigment epithelial cells, blood vessels within disorganized and thickened sensory retina, and a proliferation of benign glial cells on the vitreal surface of the lesion.
No treatment is generally indicated. Pars plana vitrectomy has been employed in a few cases to remove the epiretinal membrane, but such procedures have generally not resulted in improved vision.
COURSE AND OUTCOMES
Most such lesions are minimally progressive after detection. In the cases that appear to change during follow-up, the progression is frequently caused by contraction of the vitreoretinal surface of the lesion and not by cellular proliferation of the lesion per se. Malignant transformation of a combined hamartoma of the retina has never been documented.
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