We also identified 41 genes which were mutated specifically in transformed SCLC tumors, and 18 genes showed a mutant rate of more than 25% in 8 sequenced cases such as RB1, TP53, NOTCH2, SMAD4, PIK3R2 and EPHA3 (Fig. 2B). This evidence concerns the gene PIK3R2 and small cell lung carcinoma.