In the Ciampi et al. series [86], RAS mutations were present in 69.2% (18/26) of RET-negative cases and in only 2.5% of RET-positive sporadic MTC, confirming that activation of the RAS and RET proto-oncogenes represents alternative genetic events in sporadic MTC tumorigenesis. This evidence concerns the gene RET and medullary thyroid gland carcinoma.