Seven peptides derived from mutations detectable in single cell RNA‐seq (43.8% of total tested) induced T cell reactivity, including HCC 25 (FKBP prolyl lsomerasem8, FKBP8), HCC 33 (transformer 2 beta homolog, TRA2B), HCC 217 (hes family BHLH transcription factor 1, HES1), HCC 277 (heme binding protein 1, HEBP1; LYR motif containing 2, LYRM2), and HCC 448 (TP53; helicase with zinc finger, HELZ) (Tables S3 and S4, Supporting Information). Here, TRA2B is linked to hepatocellular carcinoma.