Mitochondrial metabolism and transcript-level regulation are increasingly recognized as important determinants of cancer biology. Among them, SLC1A5 transcript isoforms have been implicated in metabolic adaptation, but their detection remains technically challenging due to the absence of isoform-specific reagents. Here, we designed and validated a variant-specific RNA probe system capable of identifying distinct transcript isoforms in cultured cells and tissue samples. Using a carefully designed probe targeting unique isoform-specific regions, we evaluated its performance in both experimental models and clinical specimens. Preliminary analyses indicate specific detection of transcript variants, with differential expression patterns observed between tumor and non-tumor samples. These findings suggest that variant-specific RNA visualization may support biomarker development in cancer metabolism. Further studies are ongoing to assess the clinical applicability of this approach.