Aqueous Seeding in Retinoblastoma: Classification and Clinicopathologic Correlation

Abstract

To correlate the clinical types of aqueous seeds with histopathologic characteristics in primarily enucleated eyes with retinoblastoma (RB). Retrospective study. Twenty-five patients with RB. Clinicopathologic correlation of aqueous seeds in 25 eyes that underwent primary enucleation and showed evidence of aqueous seeds. Histopathologic characteristics of aqueous seeds. All 25 enucleated eyes were classified as group E RB based on the International Classification of Intraocular Retinoblastoma. Clinically, type 1 aqueous seeds were noted in 9 (36%) eyes, type 2 in 8 (32%), and type 3 in 8 (32%). Based on histopathology, type 1 seeds were defined as individual tumor cells admixed with macrophages and nonviable tumor cells. Type 2 seeds were defined as spheres and classified into 2 subtypes: (1) spheres without central necrosis containing solid clusters of tumor cells and (2) spheres with central necrosis containing a central core of necrotic cells surrounded by viable tumor cells. Type 3 seeds were defined as tumor cells admixed with macrophages and red blood cells sedimented at an angle. Aqueous seeding involved both anterior (n= 25; 100%) and posterior (n= 18; 72%) chambers. Significant infiltration of RB into the intraocular tissue (Schlemm canal, trabecular meshwork, ciliary body, choroid, optic nerve, and sclera) was noted in 23 cases (92%). Compared with eyes with type 1 and 2 seeds, eyes with type 3 seeds were more commonly associated with ciliary body infiltration (41% vs. 88%, respectively; P= 0.04). Over a mean follow-up period of 57months (median, 49 months; range, <1-175 months), metastasis and death were noted in 3 patients (12%). Similar to vitreous seeds in RB, aqueous seeds have 3 distinct histopathologic types. Posterior chamber seeds were noted in 72% of cases presenting with anterior chamber (AC) seeds, indicating the need for the treatment of both the chambers whenever conservative treatment is attempted in suitable cases. Most (92%) cases with primary aqueous seeding are associated with other high-risk histopathology features, suggesting acautious approach to conservative management in these cases.