Miscellaneous Uveal Tumors

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Chapter 154 Miscellaneous Uveal Tumors

David J. Wilson

Introduction

A great variety of primary tumors occur in the uvea. Of these, rare tumors are difficult to diagnose clinically because they often do not have enough characteristics that distinguish them from the more common tumors. However, knowledge of the epidemiologic factors, clinical features, and natural history of some of the rare tumors may allow the clinician to suspect them preoperatively. Because many of these tumors are benign, preoperative recognition could prevent or minimize surgical intervention. The more common of these overall rare tumors are covered in detail in this chapter, and their unique aspects are emphasized.

Epithelial tumors of the ciliary body: congenital

Medulloepithelioma

Medulloepithelioma (diktyoma, teratoneuroma) is a congenital tumor that is generally believed to arise from the epithelium of the medullary tube. This tumor usually arises from the ciliary body epithelium, but medulloepitheliomas of the retina and the optic nerve also occur. The first detailed histologic description of the tumor was by Verhoeff,¹ who called it a teratoneuroma, despite the absence of teratomatous features. Fuchs² reported his observations of a medulloepithelioma and coined the term diktyoma because of the netlike appearance of cells composing the tumor. Grinker³ was the first to use the term “medulloepithelioma,” which has become the preferred name because it refers to the correct cell of origin.

Three large series of medulloepitheliomas have been reported ⁴^–⁶ and provide the bulk of our knowledge of the clinical features of this tumor. In Broughton and Zimmerman’s series,⁵ the median age at occurrence of initial symptoms was 3.8 years, with a range of 6 months to 41 years. Andersen⁴ reported that the average age at the time of enucleation was 4.5 years for benign medulloepitheliomas and 7 years for malignant tumors. In the series of Canning et al.⁶ the median age at diagnosis was 3 years. In all three series, all tumors were unilateral and single, and there was no racial or hereditary predisposition.

The signs and symptoms of the 56 patients reported on by Broughton and Zimmerman ⁵ are summarized in Tables 154.1 and 154.2.

Table 154.1 Medulloepithelioma – symptoms and signs

Clinical finding	Cases (n)
Poor vision (or blindness)	22
Pain	17
Mass in iris or ciliary body	10
Leukocoria	10
Other pupillary abnormality	2
Exophthalmos (or orbital mass)	4
Enlarging globe	4
Strabismus	3
Epiphora	2
Change in color of eye	2
Hyphema	1

(Reproduced with permission from Broughton WL, Zimmerman LE. A clinicopathologic study of 56 cases of intraocular medulloepitheliomas. Am J Ophthalmol 1978;85:407–18.)

Table 154.2 Medulloepithelioma – clinical findings on initial examination

Clinical finding	Cases (n)
Cyst or mass in iris, anterior chamber, or ciliary body	30
Proptosis or orbital mass	8
Retinal mass	2
Glaucoma	26
Cataract	14
Buphthalmos	6
Iritis	4
Rubeosis	3
Retinal detachment	3
Strabismus	3
Vitreous hemorrhage	1
Hyphema	1

(Reproduced with permission from Broughton WL, Zimmerman LE. A clinicopathologic study of 56 cases of intraocular medulloepitheliomas. Am J Ophthalmol 1978;85:407–18.)

One remarkable feature of medulloepitheliomas is the frequent presence of cysts, which are formed by the production of mucopolysaccharide by the epithelial cells. These cysts can be present within the body of the tumor but also may be free-floating in the anterior or posterior chamber and vitreous (Figs 154.1–154.4). The presence of vitreous or anterior chamber cysts should alert the clinician to consider the possibility of a diagnosis of medulloepithelioma, although vitreous cysts have also been described with malignant melanoma.⁷

Fig. 154.1 External photograph showing ciliary body mass.

(Case presented by Milton Boniuk, Verhoeff Society, 1997.)

Fig. 154.2 Gross appearance of medulloepithelioma demonstrating ciliary body mass and cysts in the posterior chamber.

(Case presented by Milton Boniuk, Verhoeff Society, 1997.)

Fig. 154.3 Histopathology showing epithelial nature of the tumor with cysts formed by epithelium surrounding mucopolysaccharide-filled spaces. (H&E; ×100.)

Fig. 154.4 Histopathology demonstrating cystic spaces overlying ciliary body epithelium. (H&E; ×400.)

Another noteworthy feature of medulloepithelioma is that the intraocular pressure is frequently elevated at the time of diagnosis (see Table 154.2). This may result from secondary angle closure by the ciliary body mass, iris neovascularization, or growth of tumor cells across the trabecular meshwork.

Medulloepitheliomas usually contain, as their most significant component, sheets and cords of poorly differentiated neuroepithelial tissue. The cellular cords may line cystic spaces filled with acid mucopolysaccharide. Homer Wright and Flexner–Wintersteiner rosettes may be present, but more commonly the rosettes in medulloepithelioma are larger than those seen in retinoblastoma. Typically, the lumina of the rosettes are surrounded by multiple cell layers, which resemble primitive ciliary epithelium, rather than photoreceptors.

In addition to the neuroepithelial tissue, medulloepitheliomas may contain heteroplastic tissues, in which case they are called teratoid medulloepitheliomas. Hyaline cartilage, striated muscle, undifferentiated mesenchymal cells, and neurologic tissue resembling the brain have all been described in teratoid medulloepitheliomas.

Medulloepitheliomas may be benign or malignant. Broughton and Zimmerman ⁵ considered 66% of the tumors in their series to be malignant. Andersen,⁴ using more stringent criteria, classified 26% of the tumors in his series as malignant. From a practical point of view, even cytologically benign medulloepitheliomas can be locally invasive, extending into the iris, cornea, sclera, or orbit. For that reason all medulloepitheliomas should be considered as potentially malignant tumors, as recommended by Andersen.⁴

The initial treatment in all reported cases has been surgical – iridectomy, iridocyclectomy, or enucleation – and with total excision, the prognosis is excellent. Canning et al.⁶ have stressed the importance of attempting local resection (i.e., iridocyclectomy) only in patients with very small tumors. Of the four patients in their series who were treated by iridocyclectomy, all subsequently required enucleation. A total of 45 (80%) of the patients in Broughton and Zimmerman’s series⁵ treated by iridocyclectomy subsequently required enucleation.

In both Broughton and Zimmerman’s ⁵ and Anderson’s⁴ series of patients, the most important prognostic factor appeared to be extension of tumor into the orbit. In Broughton and Zimmerman’s series,⁵ 11 patients had extraocular extension; of this group, four died of tumor-related causes. Intracranial spread of tumor was the usual cause of death, although one patient died of lymphatic spread to the mediastinum. The effectiveness of exenteration, radiation therapy, or chemotherapy – used individually or in combination – in managing extraocular extension is not established at this time. Such methods should be considered in cases with extrascleral extension because of the high tumor-related morbidity and mortality in this group of patients.

Glioneuroma

Glioneuromas are choristomatous malformations that arise from the medullary epithelium of the anterior portion of the optic cup. They are extremely rare, and only a few cases have been reported.⁸^–¹²

Glioneuromas usually appear as a mass involving the peripheral iris and ciliary body and are usually evident within the first 6 months of life. The tumor may involve the choroid and the retina, and extraocular extension has been described. Associated ocular abnormalities are frequently present and have included persistent hyperplastic primary vitreous in the same or contralateral eye and coloboma of the iris and ciliary body. Progressive enlargement of the tumor may lead to corneal opacification, cataract, or glaucoma.

These tumors are composed of well-differentiated neural tissue, including neurons and astrocytes. All the reported cases ⁸^–¹² have eventually required enucleation because of complications of the enlarging tumor or suspected malignancy. Because this is a benign tumor, it could conceivably be managed by local resection.

Astrocytoma

Only two cases of astrocytoma of the ciliary body have been reported.^13,¹⁴ One patient was 24 years old, and the other was 52 years old. At presentation, both had solid tumors of the ciliary body, and in one patient the astrocytoma was associated with neovascular glaucoma. Growth of the tumor was not documented in either case. These tumors were probably choristomas of the anterior portion of the optic cup. Both lesions consisted of pilocytic astrocytes. Both tumors were treated by iridocyclectomy. Interestingly, in the patient with neovascular glaucoma, the rubeosis was observed to diminish after removal of the tumor.