The S784F EGFR mutation was found in a 55-year-old current heavy male smoker, with pulmonary undifferentiated NSCLC not otherwise specified....The patient was subsequently treated with docetaxel, interrupted early because of an allergic reaction, and then received erlotinib 150 mg/d. The patient was taken off erlotinib after 2 weeks due to a lung infection and then started treatment again after 2 months. A tumor progression was observed after 10 weeks at the first treatment assessment.