Firstly, we examined the expression level of TOP2A in lung adenocarcinoma and normal tissues using bioinformatics analysis of GSE10072 (tumor = 58, normal =49), GSE43458 (tumor =80, normal = 30), GSE83213 (tumor = 11, normal =46) from GEO and TCGA (tumor = 517, normal =59). The gene discussed is TOP2A; the disease is lung adenocarcinoma.