SCD5 (stearoyl-CoA desaturase 5) is a delta-9 fatty acyl desaturase that catalyzes the conversion of saturated fatty acyl-CoA substrates (palmitoyl-CoA and stearoyl-CoA) into monounsaturated fatty acids by introducing a cis double bond at the delta-9 position 123. Unlike the ubiquitously expressed SCD1 isoform, SCD5 shows tissue-specific expression, with highest levels in brain tissue across mammals 45. Beyond lipid desaturation, SCD5 participates in cellular signaling through downregulation of EGFR/AKT/MAPK and Wnt pathways, influencing neuronal proliferation and differentiation 3. SCD5 regulates visceral adipose tissue accumulation and body fat distribution through Wnt, PPAR, and C/EBP signaling 6. In cancer biology, SCD5 functions as a pro-survival factor: it is upregulated by cancer-associated fibroblasts in breast cancer and suppresses necrosis 7, while in renal cell carcinoma, VHL-mediated SCD5 downregulation shifts metabolism toward ceramide production and promotes proliferation 8. SCD5 also contributes to ferroptosis resistance through the mTORC1-SREBP1 axis in lung cancer 9. Alternative splicing generates functionally distinct isoforms (SCD5A and SCD5B) whose proportions are modulated by genetic variants 10, with implications for tumor-associated lipid metabolism reprogramming.