SLC45A3 (solute carrier family 45 member 3) functions as a proton-associated sucrose transporter capable of transporting glucose and fructose. However, its clinical significance is primarily defined by its role as a fusion partner in prostate cancer oncogenesis. SLC45A3-ERG gene fusions represent the second most common ERG rearrangement partnership in prostate cancer after TMPRSS2-ERG, occurring in approximately 6% of ERG-rearranged cases 1. SLC45A3 also forms fusions with other ETS family members including ETV5 2 and ELK4 3, with SLC45A3-ELK4 being androgen-regulated and detectable in urine of men at risk for prostate cancer 3. SLC45A3 protein expression is significantly downregulated in cancers harboring SLC45A3-ERG fusion, and this loss is associated with shorter PSA-free survival 4. Concurrent TMPRSS2-ERG and SLC45A3-ERG rearrangements combined with PTEN loss define an aggressive tumor subset never observed in low-grade, low-stage disease, suggesting these alterations could guide therapeutic decision-making 5. Emerging evidence also suggests SLC45A3 involvement in non-neoplastic vascular disease, where SLC45A3 expression correlates with GATA2 and disease penetrance in moyamoya disease 6.