Diktyoma, a clinical histological and electron-microscopical observation

Congenital neoplasms of the nonpigmented ciliary epithelium (medulloepithelioma)

BACKGROUND

Most reports on intraocular medulloepithelioma have been single case descriptions. The authors reviewed ten patients with intraocular medulloepithelioma, discuss some little known clinical features of this entity, and make diagnostic and therapeutic recommendations.

PATIENTS AND METHODS

The records of the authors' patients with histopathologically confirmed medulloepithelioma were reviewed, and the clinical features, diagnostic problems, management, histopathology, and prognosis were assessed.

RESULTS

Of the ten patients, nine were children, ranging in age from 2 months to 10 years, and one patient was 58 years of age at the time of clinical presentation. In seven patients, there was a delay in diagnosis, ranging from 3 to 28 months, and four patients underwent surgery for cataract, glaucoma, or other secondary conditions while the tumor was unsuspected. All patients had a nonpigmented ciliary body mass and a notched or subluxated lens, and six had neovascular glaucoma and evident cysts in the mass. The authors' initial management was enucleation in four patients and local resection in six. Of the six patients managed by local resection, five eventually required enucleation, four because of local tumor recurrence and one because of ocular inflammation and discomfort. Pathologically, nine tumors were classified as malignant (5 teratoid, 4 nonteratoid) and one as benign. In one patient (the adult), metastasis to the parotid gland developed.

CONCLUSION

Intraocular medulloepithelioma generally occurs in the first decade of life as a nonpigmented ciliary body mass. It has a tendency to cause secondary neovascular glaucoma, a characteristic lens notch and subluxation, and a neoplastic cyclitic membrane. Enucleation is the best treatment for advanced cases. For smaller circumscribed lesions, local resection may be attempted, but such treatment is followed frequently by local recurrence. Although most medulloepitheliomas are cytologically malignant, distant metastasis is uncommon.

Recurrent medulloepithelioma of the ciliary body. Immunohistochemical characteristics

A predominantly benign medulloepithelioma of the ciliary body was diagnosed in an 8-year-old girl and resected by iridocyclectomy. It recurred twice during 30 months. Highly malignant histopathologic features developed, and the eye finally perforated and had to be enucleated. No recurrence or metastases have subsequently developed. Histologically, the tumor was a nonteratoid medulloepithelioma consisting of elements resembling embryonic retina, nonpigmented ciliary epithelium, and neuroblasts, but had also areas of obvious glial and neuronal differentiation as judged by immunohistochemistry. The neuroepithelial tumor cells were positive for neuron-specific enolase, vimentin, and often for S-100 protein. The neuroblastic cells were generally positive for neuron-specific enolase and synaptophysin, but were intermixed with glia-like tumor cells positive for vimentin, glial fibrillary acidic protein, and S-100 protein. The results suggest that even a nonteratoid medulloepithelioma may be, unlike retinoblastoma, a truly multipotential tumor.

Medulloepithelioma diagnosed by ultrasound and vitreous aspirate. Electron microscopic observations

Ultrasonography and cytologic examination of the vitreous aspirate established the correct pre-enucleation diagnosis of medulloepithelioma in the case of an 8-year-old boy. The use of a muscle hook allowed the examiner to elevate the eye and bring the ciliary body into adequate ultrasonographic view. Histopathologic examination of the enucleated eye showed a partially pigmented mass composed of elongated neuroepithelial tubules and cords arising from the ciliary body inferiorly. Several tubules displayed a central lumen with rosette-like structures. The tumor was classified as a benign, nonteratoid medulloepithelioma. Electron microscopically the lumens of the rosettes contained myriad, slender microvilli, and were bordered by numerous terminal bar complexes and areas displaying zonula adherens and zonula occludens type junctions. Additionally, invaginating gap junctions, which clearly established that the tumor originated from the ciliary epithelium, were identified.

Malignant medulloepithelioma of the optic nerve in a horse

An 18-month-old Standardbred filly had a large intraocular tumor involving the optic nerve. The tumor was a malignant medulloepithelioma, a rare intraocular neoplasm derived from the primitive medullary epithelium. By light microscopy the tumor had cords and lobules of primitive neuroepithelial cells that formed clefts and true rosettes. Electron microscopy of the rosettes showed a girdle of zonulae adherentes joining the apices of the cells as well as several basal bodies. This is the sixth report of equine intraocular medulloepithelioma, and, to the best of our knowledge, the first intraocular medulloepithelioma arising from the optic nerve head in a horse. Massive involvement of the optic nerve should be suspected when an eye containing an intraocular mass in the posterior segment lacks light perception. In such cases a long segment of opitc nerve should be resected.

Medulloepithelioma of the ciliary body in the goldfish (Carassius auratus)

A medulloepithelioma of the ciliary body in the right eye of a 1-year-old goldfish (Carassius auratus) had spindle and epithelial cells arranged either in columns or around a central lumen. Vitreous-like material was found within the tumor. A medulloepithelioma is a most unusual tumor in fish in which ocular tumors are rare.

Malignant teratoid medulloepithelioma in a dog

A malignant teratoid medulloepithelioma that arose from the ciliary body was found in an adult Beagle. The anterior part contained relatively well-differentiated tumor cells, cartilage, and ganglion cells. These structures were interpreted as teratoid formations derived from the embryonic anlage of the medullary epithelium. The more posterior part was highly anaplastic and invasive. A transitional area contained neural rosettes of the Flexner-Wintersteiner type. This tumor is rare in both man and animals.

Synaptic lamellae in retinoblastoma

During the electron microscopic examination of the retinoblastoma in a 21-month-old girl, we found numerous synaptic lamellae and synaptic vesicles in addition to other known features. These lamellae and vesicles can be regarded as additional proof of the neural origin of retinoblastoma.

Electron microscopic diagnosis of medulloepithelioma

A 20-month-old boy with a ciliary body tumor presented with two white flocculi floating in the anterior chamber of his left eye. This material was examined by electron microscopy. Both the clinical appearance of the tumor and the ultrastructural findings suggested the diagnosis of medulloepithelioma. The flocculi contained tumor cells forming lumina and displaying neuronal-type cilia, neurotubules, and a complex band of apical desmonosomal junctions. Since the last finding is not present in retinoblastoma rosettes in the absence of fleurette differentiation, it distinguishes medulloepithelioma from retinoblastoma. The electron microscopic diagnosis has permitted a trial period of conservative cryotherapy directed at the tumor and the associated glaucoma. The electron microscopic characteristics of the tumor favor the neuroepitheliomatous and neuroblastic differentiation of medulloepithelioma rather than ependymal differentiation.

Dictyoma

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