A study by Krawczyk et al. demonstrated that activating mutations in the EGFR gene were significantly more frequent in lung adenocarcinoma bone metastases (75%) than in primary lung adenocarcinoma (12.8%, χ2  =  25.43, p  <  0.00001) or in adenocarcinoma metastasis to CNS (14.75%, χ2  =  15.09, p  <  0.0001) [201]. This evidence concerns the gene EGFR and lung adenocarcinoma.