Oxidative Stress in Retinoblastoma: Correlations with Clinicopathologic Features and Tumor Invasiveness

Purpose: Retinoblastoma (RB) is the most common primary intraocular malignancy of infancy and childhood, where tumor invasion into the choroid, optic nerve, and/or orbit are risk factors for metastasis. Here we have correlated oxidative stress with the clinicopathologic characteristics of retinoblastoma. Methods: Tumor samples were processed for histopathologic examination. Malondialdehyde, a biomarker of oxidative stress, was immunohistochemically analyzed in 34 archival retinoblastoma tumor specimens, which included 17 tumors that did not have any invasion of the choroid, optic nerve, and/or orbit, and another 17 tumors that had some form of invasion of the choroid, optic nerve, and/or orbit. Lipid peroxidation levels were biochemically measured in another cohort of retinoblastoma tissue samples (n=16), and correlated clinicopathologically. Results: Malondialdehyde immunostaining was positive in all 34/34 (100%) tumors, and their corresponding clinicopathologic features were recorded. Malondialdehyde levels were significantly higher in tumors with invasion of the choroid, optic nerve, and orbit, when compared with tumors with no invasion (p<0.05). No significant correlation was noted between malondialdehyde immunoreactivity and the differentiation/laterality of the tumors. Lipid peroxidation levels increased significantly in tumors with invasion of the choroid, optic nerve, and orbit than in tumors without invasion (p<0.05). Conclusion: RB with invasion of the choroid, optic nerve, and/or orbit strongly correlates with increased oxidative stress.