RESUMEN
Genomic profiles of tumors are often unique and represent characteristic mutational signatures defined by DNA damage or DNA repair response processes. The tumor-derived somatic information has been widely used in therapeutic applications, but it is grossly underutilized in the assessment of germline genetic variants. Here, we present a comprehensive approach for evaluating the pathogenicity of germline variants in cancer using an integrated interpretation of somatic and germline genomic data. We have previously demonstrated the utility of this integrated approach in the reassessment of pathogenic germline variants in selected cancer patients with unexpected or non-syndromic phenotypes. The application of this approach is presented in the assessment of rare variants of uncertain significance (VUS) in Lynch-related colon cancer, hereditary paraganglioma-pheochromocytoma syndrome, and Li-Fraumeni syndrome. Using this integrated method, germline VUS in PMS2, MSH6, SDHC, SHDA, and TP53 were assessed in 16 cancer patients after genetic evaluation. Comprehensive clinical criteria, somatic signature profiles, and tumor immunohistochemistry were used to re-classify VUS by upgrading or downgrading the variants to likely or unlikely actionable categories, respectively. Going forward, collation of such germline variants and creation of cross-institutional knowledgebase datasets that include integrated somatic and germline data will be crucial for the assessment of these variants in a larger cancer cohort.
RESUMEN
BACKGROUND RET p.V804M is a known activating oncogenic variant that confers an increased risk for medullary thyroid carcinoma (MTC). Based on age-specific penetrance, the American Thyroid Association (ATA) categorizes this variant as posing moderate risk. Therefore, ATA guidelines endorse prophylactic thyroidectomy for carriers in childhood (by age 5-10 years) or adulthood, or when the serum calcitonin level becomes elevated. The recommendation for thyroidectomy is increasingly controversial due to the recently reported low penetrance of the RET p.V804M variant in a large unbiased ascertainment cohort. CASE REPORT We describe the unexpected identification of this variant in a 62-year-old woman undergoing broad, multigene cancer panel testing for her personal and family history of breast cancer. There was no known family history of MTC. Biochemical screening prompted by the RET p.V804M result revealed a mildly elevated serum calcitonin. Pathology examination of her thyroidectomy specimen revealed multifocal medullary thyroid microcarcinoma; her sibling's prophylactic thyroidectomy after a RET p.V840M-positive result similarly revealed early-stage MTC. CONCLUSIONS This report demonstrates the value of genetic counseling, shared decision-making, cascade testing, and timely thyroidectomy in the management of a patient with an unexpected RET p.V804M result.
