Mechanistically, tumor cell migration is propelled by the high activity of Rho and Rac GTPases, and the specific migratory phenotype is determined by the activity of the dominant Rho family GTPases; The mesenchymal migration phenotype is primarily determined by Rac GTPase activity, while increased RhoA GTPase activity promotes ameboid migration. The gene discussed is RHO; the disease is neoplasm.