Somatic RAS mutations were found in 10 sporadic MTC patients (10/107; 9%): 3 had a mutation in K-RAS (two G12R and one G13R); one had a mutation in N-RAS (Q61L); and 6 had a mutation in H-RAS (two Q61R, one Q61K, one M72I, one G12R, and one was a novel G60D mutation, never previously reported in the literature). Here, HRAS is linked to medullary thyroid gland carcinoma.