Extraocular silicone oil deposition: a clinicopathologic case series

To characterize the clinicopathologic features of extraocular silicone oil (SO) migration in the ocular adnexae, including the conjunctiva, eyelid, and orbit (CEO). Retrospective, single-institution case series. The Florida Lions Ocular Pathology Laboratory database at the Bascom Palmer Eye Institute was searched for surgical specimens diagnosed with “silicone oil” involving the ocular adnexae from 1997 to 2023. Clinical and histopathologic features were reviewed. All specimens were stained with hematoxylin-eosin, and immunohistochemical stains for histiocytes CD68 (M1, pro-inflammatory) and CD163 (M2, anti-inflammatory). 25 specimens met inclusion criteria. Affected sites included the conjunctiva (76%), orbit (12%), eyelid (8%), and Tenon’s capsule (4%). Histopathology revealed clear dropout spaces consistent with SO surrounded by histiocytes in all cases. CD68 and CD163 both highlighted histiocytes, with CD163 demonstrating significantly higher immunohistochemical staining (p < 0.0001). The average time from SO placement to presentation was 451.1 days (Range: 14 − 1,220 days). SO migration was clinically suspected in 17 cases, presenting with conjunctival injection, irritation, cysts, or eyelid swelling. Imaging (anterior segment OCT, CT) aided diagnosis. Diagnosis of silicone oil migration in the ocular adnexae is important to avoid misdiagnosis. The presence of M2 histiocytes (anti-inflammatory) is consistent with the high immunotolerance of these lesions.