Histopathological assessment of optic nerve invasion guided by radiological findings in enucleated globes with retinoblastoma.

Abstract

Purpose: High-risk histopathological features in primary enucleated retinoblastoma globes affect the indication for neoadjuvant chemotherapy to avoid the increased risk of metastasis and to improve survival in such children. Optic nerve (ON) invasion is an important indicator of prognosis and we aim through this study to correlate the detected-ON invasion by imaging with the corresponding confirmed histopathological level of invasion. Methods: This is an approved retrospective study with collaborative agreement between the 2 centres. All enucleated globes with the diagnosis of retinoblastoma received in the histopathology department(s) from January 2015 to December 2016 (2 years) were collected for review by 2 pathologists and the charts were reviewed for basic demographic data. All patients underwent Magnetic resonance imaging (MRI) under sedation upon diagnosis and MRI reading was done by an experienced single neuroradiologist. Results: A total of 38 patients were included: 21 males and 17 females. 29 (77.3%) had unilateral involvement, 7 (18.4%) had bilateral involvement and 2 cases had trilateral disease. The overall mean age at diagnosis was 22.63 ±15.15 months. 28 cases (74%) had pathologically-proven ON invasion: prelaminar (31.6%), laminar (18.4%), and post-laminar (23.7%). Post-laminar ON invasion was identified in 8 cases (true positive), while another 8 were false positive. Only 1 case was missed on MRI (accuracy: 63.3%; sensitivity: 88.9%; specificity: 72.4%; Positive predictive value (PPV): 50%; Negative predictive value (NPV): 95.5%). Conclusions: MRI was found to be less sensitive in evaluating pre-laminar and laminar ON invasion (0.0 and 42.9%) compared to post-laminar invasion (88.9%) but had better specificity in detecting various levels of invasion (72.4 to 83.9%). Obtaining deeper histologic sections in some cases where there are mismatching ON level of invasion between MRI and histopathological examination is recommended to avoid misleading assessment of the high-risk histopathological features. There are no solid international protocols of how many sections should be obtained to evaluate the optic nerve invasion in these globes and this should be established for universal use especially in less developed countries where experienced pathologists might be lacking. Key words: Retinoblastoma; High-risk, Histopathology; Optic nerve invasion; Lamina cribrosa; Radiology; Magnetic resonance imaging; Chemotherapy.