Direct sequencing of 9 parosteal osteosarcomas, including 3 of low grade and 6 with dedifferentiation, revealed activating GNAS mutations in 5 cases (55%), distributed as 4 R201C-mutated tumors and 1 tumor with an R201H mutation.
To ascertain the frequency in colon cancer we employed a sensitive pyrosequencing platform for mutation detection of the R201C and R201H GNAS hotspots in tumor samples representing all clinical stages.
Molecular screening failed to find mutations in RAS, TP53, and BRAF hot spots, whereas Arg201His mutation in GNAS gene (gsp oncogene), absent in the previous surgical materials, was detected in the tumor from the last surgery, which was found to be monoclonal.