Retinoblastoma with MYCN Amplification Diagnosed from Cell-Free DNA in the Aqueous Humor.

INTRODUCTION

The objective of this study was to report the clinicopathologic features of three cases of -amplified retinoblastoma identified genetically by aqueous humor sampling.

METHODS

Whole-genome sequencing was performed using isolated cell-free DNA (cfDNA) from aqueous humor of 3 retinoblastoma patients. We analyzed genomic copy number and mutational alterations, histologic and pathologic features, and clinical data.

RESULTS

The most common genetic alteration identified in these three retinoblastoma cases was a focal amplification on 2p. All tumors showed an early age of diagnosis with a median of 9 months. The tumor histopathologic features included neovascularization and subretinal seeding in case 1, diffuse nature with choroidal and prelaminar optic nerve invasion in case 2, and complete vitreous seeding in case 3. Case 1 expressed RB protein and had no mutation, case 2 did not express RB protein and had an mutation, and case 3 did not express RB protein and likely had an epigenetic effect on RB expression.

CONCLUSIONS

Our report shows 3 cases of unilateral retinoblastomas diagnosed in patients ranging from 4 months to 18 months old. Genomic analysis from AH cfDNA revealed amplification with intact RB protein staining in case 1 and lack of RB staining in cases 2 and 3. mutational analysis in the AH confirmed a pathogenic variant in case 2. Clinical pathology showed features requiring aggressive treatment, specifically enucleation.

IMPORTANCE

-amplified retinoblastomas demonstrate unique pathogenesis and aggressive behavior, regardless if is a primary or secondary driver of disease. Genomic analysis from aqueous humor may be useful when deciding to enucleate as opposed to treating conservatively. Focal amplification on 2p might be relevant for tumor growth in this subset of the retinoblastoma population in terms of targeted therapeutics.