Résumé
Background: Medullary thyroid carcinoma (MTC) may occur either as a sporadic or familial disease. Multiple endocrine neoplasia (MEN) type 2, inherited as an autosomal dominant disease, is characterized by MTC only (FMTC) or coexistence of MTC with other endocrine neoplasia (NEM 2A, 2B). Germline mutations of the RET proto-oncogene (cRet) are found in the inherited forms and in some apparently sporadic MTC cases. Aim: To study RET mutations in 8 families with MEN 2. Material and methods: RET mutations were screened in peripheral blood DNA from 18 patients and 87 high risk carriers belonging to 8 MEN 2 families and 52 sporadic MTC. Exons 10, 11, 13, 14, 15 and 16 of the c-Ret were amplified by polymerase chain reaction (PCR) and examined by direct sequencing of PCR products and/or restriction enzyme analysis. Results: Five MEN 2A and one FMTC families with a germline mutation at codon 634, one MEN 2A and one FMTC family carrying a mutation at codon 620 were identified. Mutations were found in 23 out of 87 high risk carriers. In addition, we detected a S891A (exon 15) germline mutation in a sporadic MTC patient and in one out of her three sons and V804M (exon 14) in another sporadic MTC case and in one out of his six relatives, indicating in both cases the presence of a sporadic misclassified familial disease. Conclusions: These results underscore the importance of routine application of c-Ret testing in all cases of MTC either familial or sporadic