Expression disorders of early NSCLC. (A) PCA analysis before batch effect removal. (B) PCA analysis following batch effect removal. (C) Differentially expressed gene (DEG) volcano map. Red nodes represent upregulated genes, blue nodes represent downregulated genes, and gray nodes represent no differentially expressed genes. (D) Hierarchical clustering dendrograms of the expression patterns of differently expressed genes that distinguish between NSCLC and normal lung tissue.