The leading differential diagnoses included retinoblastoma, medulloepithelioma and juvenile xanthogranuloma.
The cytopathology report revealed small round cells with uniform nuclei and scanty cytoplasm, consistent with medulloepithelioma. There were no teratomatous or sarcomatous elements. There were also no mitotic figures. The specimen did not display any malignant features.
Three treatment options were considered. The first was iridocyclectomy; however, the lesion was too extensive and not amenable to excision. The next was enucleation. This was discussed in detail with the parents as an option. The parents were made aware of the high recurrence rate of medulloepithelioma following local resection, often resulting in enucleation. The last option was plaque radiotherapy, which was ultimately chosen.
An iodine-125 boomerang plaque was surgically placed, encompassing five clock hours of the ciliary body regions, completely covering the entire extent of the tumor. An apex dose of 60 Gy was delivered over four days.
On follow up, the tumor thickness reduced slowly from 3.1 mm originally to 2.6 mm at two months and 2.4 mm at four months. There were no complications on short follow-up, but cataract is anticipated.
Discussion
Medulloepithelioma is a rare ciliary body neoplasm usually presenting before the age of 10 years. It is an embryonal tumor derived from the inner layer of the optic cup. It is typically characterized as nonteratoid or teratoid. Nonteratoid tumors involve medullary epithelial cells only, while teratoid tumors contain skeletal muscle, brain elements or cartilage. Medulloepithelioma can show benign or malignant features. These tumors rarely metastasize but can spread locally and have a high recurrence rate within the eye if local resection is performed.
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A review of prevalence and mechanisms of secondary intraocular pressure elevation in eyes with intraocular tumors revealed high pressure in 17 percent of eyes with retinoblastoma and nearly all eyes with medulloepithelioma. Secondary glaucoma is a consistent feature of medulloepithelioma, most related to iris neovascularization.
In one series of seven patients from the Wills Eye Ocular Oncology Service with medulloepithelioma, five had neovascular glaucoma and two had tube shunts placed prior to detection of the intraocular mass. Medulloepithelioma should be highly suspected in any child with unexplained iris neovascularization.
Histopathologic evaluation reveals poorly differentiated round cells with scant cytoplasm. These cells form ribbon-like structures demonstrating polarity and produce a mucinous substance forming cysts. Malignant characteristics include poorly differentiated cells resembling retinoblastoma cells, areas that resemble sarcoma, presence of mitotic activity and local invasion.
Treatment options primarily include local resection, plaque radiotherapy and enucleation. For tumors with a cyclitic membrane, free-floating cysts and a friable appearance, enucleation is recommended. For small tumors without the aforementioned characteristics, local resection can be attempted, with the understanding of the possibility of future recurrence. Plaque therapy is another conservative option, as performed in this case.
The recurrence rate following resection can be problematic. One explanation is that the sheet of proliferating tumor cells on the hyaloid face could be left behind during local resection. In a case series from the Wills Eye Ocular Oncology Service of 10 patients with medulloepithelioma, four were managed with primary enucleation and six with local resection. In the long term, five of six eventually came to enucleation for recurrence. The one patient that avoided enucleation did have a small recurrence that was controlled with cryotherapy.
In conclusion, any child with unexplained neovascularization of the iris should be suspected of having an intraocular tumor, such as medulloepithelioma, until proven otherwise. These patients should be thoroughly examined to rule out medulloepithelioma. REVIEW
The author would like to thank Carol L. Shields, MD, Wills Eye Institute Ocular Oncology Service, for her assistance with this case.
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