Medullary thyroid carcinoma (MTC) occurs sporadically (sMTC) or as part of the 
inherited cancer syndrome, multiple endocrine neoplasia type 2 (MEN 2). While 
the occurence of the MEN 2 syndrome is associated with mutations in the RET 
protooncogene, the reason for carcinogenesis in sMTC still remains unclear. Ras 
is a frequently mutated oncogene in a broad spectrum of human tumors and has 
been found in about 50% of follicular, papillary or anaplastic thyroid 
carcinomas. The purpose of this study was to determine, whether mutations in the 
ras oncogene could play a possible role in the carcinogenesis of sMTC. In this 
study we analyzed 15 sMTC for mutations in the hotspots codon 12, 13 and 61 of 
the H- and K-ras oncogene. We used the direct sequencing technique. In none of 
the examined tumors we were able to detect a mutation in the codon 12, 13 and 61 
of the H-ras and K-ras oncogene. Based upon these results, we conclude that H- 
and K-ras do not play an important role in the carcinogenesis of sMTC.