Histopathologic Observations After Intra-arterial Chemotherapy for Retinoblastoma

Objective: To describe histopathologic observations in eyes enucleated after intra-arterial chemotherapy (IAC) for retinoblastoma (Rb). Methods: Retrospective histopathologic analysis of 8 eyes. Results: The eyes were enucleated for tumor viability (n = 4), neovascular glaucoma (n = 2), anaphylactic reaction from IAC (n = 1), and persistent retinal detachment with poor visualization of the tumor (n = 1). Of the 2 eyes judged clinically with complete tumor regression and the 5 with viable tumor, the findings were confirmed on histopathology. The Rb response ranged from minimal (n = 1) to moderate (n = 1) to extensive (n = 4) to complete regression (n = 2). Viable vitreous seeds (n = 4 eyes), invasion into the optic nerve (n = 3), reaching the lamina cribrosa in 2 cases, and invasion into the choroid (n = 1) were observed. Histopathologic evidence of ischemic atrophy involving the outer retina and choroid was found in 4 eyes. One eye treated at another center with IAC and enucleated by our team for recurrence was observed to have extensive choroidal and outer retinal atrophy. This case showed orbital vascular occlusion and subendothelial smooth muscle hyperplasia. Intravascular birefringent foreign material was observed in 5 cases within occluded vessels, stimulating a granulomatous inflammatory response. The foreign material comprised cellulose fibers (n = 3), synthetic fabric fibers (n = 1), or unknown composition (n = 2). Thrombosed blood vessels were identified in 5 eyes and involved ciliary arteries in the retrobulbar orbit (n = 5), scleral emissarial canals (n = 1), small choroidal vessels (n = 1), and central retinal artery (n = 1). Conclusion: Retinoblastoma can be controlled with IAC, but histopathology of enucleated eyes reveals that ocular complications including thromboembolic events can occur.