Intraocular Schwannoma

Abstract

Schwannoma is a proliferation of neoplastic Schwann cells. Whereas schwannomas of the head and neck region are common, intraocular tissues are rarely affected. Uveal schwannoma has been aptly called a "pseudomelanoma", reflecting the difficulty in its clinical distinction from uveal malignant melanoma. Most of our current knowledge on intraocular schwannoma is limited to case reports, short case series, and non-comprehensive literature reviews. Three isolated reports of uveal schwannoma with extrascleral extension exist in literature, but the prognostic significance of this growth pattern is unknown. We present a patient with choroidal schwannoma with extrascleral extension and review 46 previously reported cases of uveal schwannomas to delineate clinical and pathologic characteristics of these intraocular tumors with a specific emphasis on schwannoma with extraocular extension.

Uveal schwannoma in a brown‐eyed dog

“…However, in this dog, the tumor did not have any extrascleral involvement, suggesting it exhibits a less aggressive biological behavior, and thus, distant metastasis is less likely. The patchy and faint staining for S‐100 in this dog's tumor is similar to that reported in malignant schwannomas in humans; however, it is important to recognize that this relationship has not been proven in dogs …”

“…Schwannomas and neurofibromas are peripheral nerve sheath tumors (PNST) that arise from either Schwann cells or neurofibroblasts and most commonly occur in the head, neck, and orbit . These tumors are rarely noted intraocularly in people, accounting for 0.1% of all intraocular tumors in one retrospective study .…”

“…In the human literature, the overall metastatic rate of intraocular schwannomas is low with this entire tumor class being rare . In the single documented metastatic case report, the tumor was considered exhibited more aggressive behavior as it demonstrated extrascleral invasion, which is associated with locally aggressive schwannomas in people . The case reported by Duke et al .…”

“…Peripheral nerve sheath tumors are most commonly found on the head and neck regions of both dogs and people . While less common, schwannomas, a subset of peripheral nerve sheath tumors arising from Schwann cells, have been found in the iris, ciliary body, and choroid in people . Zarfoss et al .…”

Intraocular schwannoma: A case series of 3�patients

“…Intraocular schwannomas are benign encapsulated tumors consisting of a pure proliferation of Schwann cells and are not life threatening; however, they can cause impairment and blindness via tumor growth and serous retinal detachment, and appropriate treatment is required to prevent vision loss and progressive enlargement of the condition (8)(9)(10). Uveal schwannoma is also termed a 'pseudomelanoma', as it simulates the most common type of primary intraocular tumor, uveal melanoma; this term reflects the difficulty in clinically distinguishing the schwannoma from uveal malignant melanoma (11)(12)(13). In certain previously reported cases, eyeball enucleation was performed due to a diagnosis of malignant melanoma, and only after subsequent histopathological examination of the surgical specimen was a benign tumor revealed (14)(15)(16)(17)(18).…”