The χ2 test revealed that clinical stage (X3), degree of differentiation (X4), lymph node metastasis (X5), pleural effusion (X7), family history of cancer (X8), occupational exposure (X9), surgery (X11) and radiotherapy (X12) were not associated with an increased risk of EGFR mutation. The gene discussed is EGFR; the disease is Pleural effusion.