Aqueous Seeding in Retinoblastoma: Classification and Clinicopathologic Correlation

Abstract

Purpose: To correlate the clinical types of aqueous seeds with histopathologic characteristics in primarily enucleated eyes with retinoblastoma (RB).

Design: Retrospective study.

Participants: Twenty-five patients with RB.

Methods: Clinicopathologic correlation of aqueous seeds in 25 eyes that underwent primary enucleation and showed evidence of aqueous seeds.

Main outcome measures: Histopathologic characteristics of aqueous seeds.

Results: 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 57 months (median, 49 months; range, <1-175 months), metastasis and death were noted in 3 patients (12%).

Conclusions: 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 a cautious approach to conservative management in these cases.

Keywords: Aqueous seeds; High-risk features; Histopathology; Intracameral chemotherapy; Retinoblastoma.