Here we focused on TIAM1’s function in NE SCLC owing to its higher expression in this SCLC type compared to non-NE SCLC, as well as in the NE component of CDX transition models, and that TIAM1 is the only RAC-selective GEF enriched in NE SCLC cells. This evidence concerns the gene TIAM1 and small cell lung carcinoma.