Germline mutations of the RET proto-oncogene localized on chromosome 10q11.2 are the underlying cause of hereditary medullary thyroid carcinoma. In MEN 2A and FMTC, mutations can be found in exons 10, 11, 13 or 14. MEN 2B is characterized by a specific mutation in exon 16. In a significant number of sporadic MTC somatic mutations in codon 918 (exon 16) are detectable. Some rare sporadic MTC present somatic mutations in codons 611, 634, 768 and 883. Recently, deletion-insertion of the RET proto-oncogene in exon 11 and a deletion in exon 10 has been found. RET proto-oncogene mutations are not only responsible for the development of the familial MTC, but may also play an important role in the pathogenesis of sporadic MTC. However, the prognostic relevance of these somatic events is still unclear.
