Background <p>Retinoblastoma (RB) is a pediatric ocular malignancy with a high prevalence of advanced-stage presentation in developing countries, often resulting in CNS metastasis. Standard diagnostic tools, such as imaging techniques and cerebrospinal fluid (CSF) cytology, have limitations in detecting minimal tumor dissemination. GD2 synthase, a key enzyme that controls ganglioside synthesis, has been proposed as a promising marker for tumor dissemination in various cancers but its relevance in RB remains unexplored. This study evaluates GD2 synthase expression in RB tumors and CSF samples to assess its association with poor prognosis.</p> Methods and results <p>The expression of GD2 synthase was initially evaluated in the RB tumors (<i>n</i> = 7) and control neural retina (<i>n</i> = 7) using RT-qPCR. Subsequently, RB patient CSF samples (<i>n</i> = 30) were collected and RNA isolation was done using Trizol-choloroform method. The GD2 synthase copy number were determined using absolute quantification and clinically correlated. GD2 synthase showed significant upregulation in RB tumors compared to neural retina (p value = 0.020). Interestingly, a significant positive correlation was observed between increased GD2 synthase copy number in patient CSF samples with invasive features (p value = 0.023).</p> Conclusions <p>The present study suggests that RB patients with elevated GD2 synthase expression are at higher risk of tumor invasion and poor prognosis. Integrating the analysis of GD2 synthase expression with routine cytological examination could improve overall disease management.</p>