present as large retinal inflammatory masses with diffuse vitritis and simulate endophytic retinoblastoma. It also may resemble exophytic retinoblastoma by presenting as a solitary subretinal granuloma with little vitreous reaction. These chorioretinal masses most commonly are located in the peripheral fundus and produce vitreoretinal bands that can extend from the masses to the optic disc. Contraction of these vitreoretinal membranes can lead to tractional retinal detachments that are extremely rare in eyes with retinoblastoma. Ultrasonography that demonstrates vitreous traction bands or tractional retinal folds or detachments are characteristic of ocular toxocariasis (see the article by Ventura and colleagues, elsewhere in this issue).

Medulloepithelioma

Medulloepithelioma is a nonhereditary congenital tumor that typically manifests during the first

decade of life.5 It most commonly arises from the ciliary body.6 Involvement of the iris and optic nerve, however, has been reported.7–10 Medulloepithelioma is an important differential diagnosis of leukocoria. It presents as an irregular white or gray translucent mass. The presence of cysts within the tumor is a characteristic feature. Large cysts may break off from the tumor and float freely in the anterior chamber or vitreous cavity. A scan shows mainly high internal reflectivity with medium spike height from cystic areas. On B-scan, these lesions are often dome-shaped, highly reflective with irregular internal structures. Cystic spaces can be demonstrated in some lesions (Fig. 6).

BENIGN UVEAL TUMORS

Iris and Ciliary Body Nevus

Iris and ciliar ciliary (spell) body nevus are evaluated best by ultrasound biomicroscopy, which should be used to determine tumor size, posterior