We present the case of a 20-year-old male with a clinicalpresentation of both glioblastoma multiforme and multiple adenomatous colonic polyps.The molecular genetics study revealed a mutation in KrasAsp12 gene and altered expression of HMSH2 and HMSH6 proteins encoded by the DNA mismatch repair genes in two of the colonic polyps. The gene discussed is MSH2; the disease is colon inflammatory polyp.