Positive Germline Selection in Pedigrees With Multiple Endocrine Neoplasia Type 2 Carrying V804M Mutation in the RET Gene.

BACKGROUND: Multiple endocrine neoplasia (MEN) type 2 is an autosomal dominant cancer syndrome associated with the development of thyroid cancer and tumors or hyperplasia in other endocrine organs. It is caused by mutations in the RET gene and can be phenotypically classified into MEN types 2A and 2B. MEN2B is often sporadic resulting from a spontaneous mutation, M981T. A positive paternal germline selection has been reported for this mutation. METHODS: We analyzed the V804M mutation in the RET gene which also affects the intracellular domain of the protein but results in a different phenotype, MEN2A. We compared the observed and expected frequencies of the V804M mutation and the paternal and maternal germline transmission frequency of V804M mutation in three previously reported multigenerational families. RESULTS: Our analysis indicates that the observed frequency of the V804M mutation is significantly greater than the expected frequency suggesting positive germline selection (P < 0.001). Furthermore, comparative analysis of observed versus expected transmission frequencies from affected parents shows a higher maternal germline transmission frequency (P = 0.001). CONCLUSIONS: Our results suggest that in the RET gene, positive germline selection may extend to mutations other than M918T and, furthermore, at least for the V804M mutation in these families, there is evidence for maternal germline selection.

NSGC practice guideline: risk assessment and genetic counseling for hereditary breast and ovarian cancer.

PURPOSE: The purpose of this document is to present a current and comprehensive set of practice recommendations for effective genetic cancer risk assessment, counseling and testing for hereditary breast and ovarian cancer. The intended audience is genetic counselors and other health professionals who care for individuals with, or at increased risk of, hereditary breast and/or ovarian cancer.

Single nucleotide polymorphisms act as modifiers and correlate with the development of medullary and simultaneous medullary/papillary thyroid carcinomas in 2 large, non-related families with the RET V804M proto-oncogene mutation.

BACKGROUND: Single nucleotide polymorphisms (SNPs) may function as modifiers of the RET proto-oncogene, resulting in the expression of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC). We present 2 non-related Italian-American families (Family 1, n = 107; Family 2, n = 31) with the RET V804M mutation. We have correlated the presence of specific SNPs and the rare RET V804M mutation to MTC, C-cell hyperplasia (CCH), and PTC. METHODS: Sequencing was performed on exons 10, 11, and 13-16 of the RET proto-oncogene. The presence of MTC, CCH, and PTC were correlated to specific SNPs. RESULTS: In both families, 3 SNPs in exon 11 (G691S), exon 13 (L769L), and exon 15 (S904S) were detected in 100% of patients with overt MTC. The SNP L769L was present in all patients including patients with PTC, MTC, and CCH. CONCLUSION: SNP analysis revealed a similar pattern between the 2 families. SNPs in exon 11 (G691S) and exon 15 (S904S) appear to influence the development of MTC. A SNP in exon 13 (L769L) may serve as a modifier in the development of simultaneous MTC and PTC, as well as presentation of MTC, in patients with the RET V804M mutation.

Risk assessment and genetic counseling for hereditary breast and ovarian cancer: recommendations of the National Society of Genetic Counselors.

These cancer genetic counseling recommendations describe the medical, psychosocial and ethical implications of identifying at-risk individuals for hereditary breast and ovarian cancer (HBOC) through cancer risk assessment, with or without genetic susceptibility testing. They were developed by members of the Practice Issues Subcommittee of the National Society of Genetic Counselors' Familial Cancer Risk Counseling Special Interest Group. The information contained in this document is derived from extensive review of the current literature on cancer genetic risk assessment as well as the professional expertise of genetic counselors with significant experience in education and counseling regarding hereditary breast and ovarian cancer. Critical components of the process include the ascertainment of medical and family histories, determination and communication of cancer risk, assessment of risk perception, education regarding the genetics of HBOC, discussion of molecular testing for HBOC if appropriate (including benefits, risks and limitations) and any necessary follow-up. These recommendations do not dictate an exclusive course of management or guarantee a specific outcome. Moreover, they do not replace the professional judgment of a health care provider based on the clinical situation of a client.