High Prevalence of <i>RAS</i> Mutations in <i>RET</i> -Negative Sporadic Medullary Thyroid Carcinomas

Overall, our results showed that RAS mutations were present in 68.0% (17 of 25) of the RET-negative MTC and in only 2.5% of the RET-positive MTC (P < 0.0001), suggesting that activation of the protooncogenes RAS and RET represents alternative genetic events in sporadic MTC tumorigenesis.