Features of patients with hereditary mixed polyposis syndrome caused by duplication of GREM1 and implications for screening and surveillance by Lieberman, S, Walsh, T, Schechter, M, Adar, T, Goldin, E, Beeri, R, Sharon, N, Baris, H, Ben Avi, L, Half, E, Lerer, I, Shirts, B, Pritchard, C, Tomlinson, I, King, M, Levy-Lahad, E, Peretz, T, Goldberg, Y