SMAD4 is a tumor suppressor gene and it encodes an intracellular mediator in the transforming growth factor b (TGF b) signal transduction pathway. SMAD4 mutations are very rare in glioblastoma and are present in less than 1% of cases and the significance of these mutations are unclear in this tumor type. The effect on protein function of SMAD4 P472T remains to be further elucidated. These results should be interpreted in the clinicopathologic context.