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A 13-year-old boy presented with a pigmented lesion on his iris. He had sustained a sports-related blunt trauma injury to his left eye, but he was not experiencing any symptoms, according to Carol L. Shields, MD, of Thomas Jefferson University in Philadelphia, and co-authors.

On examination, the patient's best-corrected visual acuity was 20/20 OU, and both eyes had normal intraocular pressure, the team reported in

A slit lamp examination showed that the right eye was normal; however, his left eye had a round, pigmented lesion, 3 × 3 mm in basal dimension, which revealed gravitational shifting within the anterior chamber fluid when the patient tilted his head. There was no evidence of corneal guttatae or swelling.

"Anterior segment optical coherence tomography depicted the lesion in the anterior chamber angle abutting the corneal endothelium and resting on the iris stroma with no internal fluid level and no solid component," noted Shields and team.

An ultrasound biomicroscopy was performed, which showed that the lesion was cystic, and thickness was 1.6 mm. Findings of a dilated fundus examination were normal for both eyes.

The team described several approaches to diagnosis and potential management of the lesion. Performing a biopsy with fine needle aspiration, followed by cytology and cytogenetic analysis, were not indicated, they explained, since the cystic nature of the lesion and its location outside the iris made iris melanoma unlikely.

Likewise, its likely benign nature meant that iodine 125 plaque radiotherapy was not appropriate. The lesion's asymptomatic nature and absence of impact on visual axis eliminated the need for cyst paracentesis with complete drainage. Furthermore, the authors pointed out that draining a free-floating cyst with no point of attachment to the iris "would likely prove to be technically difficult."

"There was no expectation that this cyst would grow, rupture, transform into a malignant process, or cause damage to the cornea," Shields and colleagues wrote. They diagnosed the patient with a free-floating iris pigment epithelium (IPE) cyst, and determined that there was no need for further testing or intervention.

The team counseled the young patient regarding the benign nature of the cyst, and advised him to return in 12 months for follow-up with repeated imaging examinations.

Discussion

Shields and co-authors pointed out that while a pigmented mass located in the anterior chamber could be benign, it has the potential to be a malignant entity, such as iris melanoma.

Tumors of the iris are generally classified as solid (79% of cases) or cystic (21% of cases). Among solid tumors, there are of melanocytic lesions: the most common, benign iris nevus, accounts for about 60% of cases, followed by iris melanoma (26%), and iris freckle (4%).

"Cystic iris tumors are subclassified based on their tissue layer of origin, arising from either the iris stroma or iris pigment epithelium (IPE)," Shields and colleagues wrote. Iris stromal cysts tend to affect young children; these cysts are translucent with a smooth lobulated surface, and occur on the anterior surface of the iris. In contrast, IPE cysts develop on the posterior surface of the iris and resemble a solid melanocytic tumor -- such as iris melanoma or IPE adenoma -- due to their brown or black color.

Shields and colleagues said that, historically, this has resulted in some IPE cysts being mistakenly diagnosed as melanoma, which in some cases has even resulted in enucleation. Because iris melanoma is a malignant tumor with the potential to metastasize, "proper treatment for life protection with consideration of the potential for ocular adverse sequelae should be realized. Differentiation of the various iris tumors is paramount to management," they noted.

The characterization of iris tumors and differentiation of solid from cystic tumors are best achieved using ultrasound biomicroscopy and anterior segment optical coherence tomography. "These are critical for defining tumor basal dimension and thickness to monitor change over time or response to treatment," the authors wrote.

In this patient's case, gravitational shifting of the mass was revealed on slit lamp biomicroscopy, while its cystic nature and the absence of a solid component and internal fluid were evident on both ultrasound biomicroscopy and anterior segment optical coherence tomography. The case report included a video, which authors noted "demonstrates the superior-to-inferior descent of an IPE cyst across the visual axis, coursing purely through the aqueous humor with gravity, offering insight into the dynamic behavior of this lesion."

"In summary, free-floating IPE cysts are benign epithelial cysts that can dislodge into the aqueous or vitreous following , as in this patient," Shields and co-authors concluded. Because they are benign and rarely associated with decompensation of the endothelium or effects on vision, or other adverse sequelae, conservative observation is the best approach in these cases.

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