To develop this method, we enriched the cell surface–presented HLA class I-bound peptides in two primary melanoma cell lines, two EGFR-mutant lung adenocarcinoma cell lines, and one primary tumor from an EGFR-mutant patient who had undergone EGFR tyrosine kinase inhibitor therapy and identified those peptides using high-resolution tandem MS (MS/MS). The gene discussed is EGFR; the disease is lung adenocarcinoma.