Accuracy of family history of cancer:clinical genetic implications

Family medical history is the cornerstone of clinical genetic diagnosis and management in cases of familial cancer. The soundness of medical decisions can be compromised if reports by the family on affected relatives are inaccurate. Although very time consuming, family medical histories are therefore routinely verified. To investigate whether such verification is clinically justified, we retrospectively analysed the accuracy of a consecutive series of 383 tumour reports from counsellees on 120 families in our clinic. We evaluated these families for the impact of verification on clinical genetic diagnosis and management. Accuracy according to cancer type showed marked variation, ranging from 93% and 89% for breast cancer and colorectal cancer, respectively, to 42% and 37% for extra-colorectal alimentary tract cancer and uterine cancer. Accuracy was related to the degree of kinship of the affected relative, but not to age and gender of the counsellee, nor to the reason for referral or personal history of cancer. Age at diagnosis and multiple primary tumours were reported accurately in 97% and 94% of cases, respectively. In six out of 120 families verification data changed clinical genetic management, in five of these the genetic risk was reduced. Although verification of all reported cancer cases in a family remains the 'gold standard' for clinical as well as research purposes, verification of reports on breast cancer can be limited without seriously compromising medical decision making. In cases where verification is impossible because medical records are unavailable, findings from studies such as ours may help in interpreting family histories

Molecular and clinical characteristics of MSH6 variants: An analysis of 25 index carriers of a germline variant

The MSH6 gene is one of the mismatch-repair genes involved in hereditary nonpolyposis colorectal cancer (HNPCC). Three hundred sixteen individuals who were known or suspected to have HNPCC were analyzed for MSH6 germline mutations. For 25 index patients and 8 relatives with MSH6 variants, molecular and clinical features are described. For analysis of microsatellite instability (MSI), the five consensus markers were used. Immunohistochemical analysis of the MLH1, MSH2, and MSH6 proteins was performed. Five truncating MSH6 mutations, of which one was detected seven times, were found in 12 index patients, and 10 MSH6 variants with unknown pathogenicity were found in 13 index patients. Fourteen (54%) of 26 colorectal cancers (CRCs) and endometrial cancers showed no, or only weak, MSI. Twelve of 18 tumors of truncating-mutation carriers and 3 of 17 tumors of missense-mutation carriers showed loss of MSH6 staining. Six of the families that we studied fulfilled the original Amsterdam criteria; most families with MSH6, however, were only suspected to have HNPCC. In families that did not fulfill the revised Amsterdam criteria, the prevalence of MSH6 variants is about the same as the prevalence of those in MLH1/MSH2. Endometrial cancer and/or atypical hyperplasia were diagnosed in 8 of 12 female carriers of MSH6 truncating mutations. Most CRCs were localized distally in the colon. Although, molecularly, missense variants are labeled as doubtfully pathogenic, clinical data disclose a great resemblance between missense-variant carriers and truncating-mutation carriers. We conclude that, in all patients suspected to have HNPCC, MSH6-mutation analysis should be considered. Neither MSI nor immunohistochemistry should be a definitive selection criterion for MSH6-mutation analysis