Screening of RET gene mutations in Chinese patients with medullary thyroid carcinoma and their relatives.

The rearranged during transfection (RET) gene is a proto-oncogene; active mutations frequently occur in medullary thyroid carcinoma (MTC). This study investigated the spectrum of germline RET mutations and clinical features in Chinese hereditary MTC patients. A total of 53 family members from 11 different hereditary MTC families were recruited for detection of RET exon 8, 10, 11, 13, 14, 15, and 16 mutations, in genomic DNA from peripheral blood leucocytes using polymerase chain reaction (PCR) and direct DNA sequencing. Of the 53 participants, eight different germline RET mutations were detected in 37 individuals. These RET mutations were distributed in exons 10, 11, 13, and 16. The most frequent RET mutation was localized at exon 11 codon 634 (67.6 %; 25/37) and the most prevalent mutation was C634R (37.8 %; 14/37). The most frequent phenotype was multiple endocrine neoplasia type 2A (MEN2A). The incidences of MTC, pheochromocytoma, and hyperparathyroidism in the MEN2A patients were 100, 36.4 and 18.2 %, respectively. The phenotype of families with Y606C or L790F mutation was categorized as familial medullary thyroid carcinoma. Moreover, one proband was identified with multiple endocrine neoplasia type 2B and carried a de novo mutation of M918T. Two families with C618S/Y mutation were categorized as unclassified multiple endocrine neoplasia type 2. Our results further substantiate that most germline mutations of the RET proto-oncogene were localized at codon 634 in Chinese hereditary MTC patients and carriers. RET mutation at codon 634 was always associated to the phenotype of MEN2A. Screening of RET mutations should be probably limited to exons 10, 11, 13 and 16 initially to be cost-effective in China.