We performed the DEGs analysis between blood‐CTCs and CSF‐CTCs of four BC‐LM patients, 8 genes (SMIM22, MDK, NPDC1, PLPP2, METRN, SCD, BICDL2, NR2F2) were significantly upregulated both in CSF‐CTCs compared to blood‐CTCs (adjusted P‐value < 0.05, FoldChange > 1.5, Figure S13C,D), deserving attention and further study. The gene discussed is METRN; the disease is breast cancer.