Two with EGFR-p. Q787Q (SNP ID, rs10251977; c.2361G>A) synonymous mutation in exon 20 were responsive to erlotinib therapy in the second-line setting after first-line chemotherapy. To the best of our knowledge, the present two cases are the first to be reported with lung adenocarcinoma with EGFR-p. Q787Q synonymous mutation responding to erlotinib.….We suggest that this rare synonymous mutation (EGFR-p. Q787Q) is a sensitive EGFR mutation in NSCLC.