Lynch syndrome caused by MLH1 mutations is associated with an increased risk of breast cancer: a cohort study.

INTRODUCTION: Lynch syndrome is known to cause an increased risk of malignancies, including bowel and endometrial cancers. However, the risk of breast cancer associated with mutations in the mismatch repair (MMR) genes that cause Lynch syndrome is still unclear. MATERIALS AND METHODS: This study assesses the cumulative risk of breast cancer in 106 MLH1 and 118 MSH2 families. Families were referred on the basis of clinical criteria. Pedigree information was obtained, and tumour immunohistochemistry and microsatellite testing performed. Appropriate patients underwent sequencing and multiple ligation dependent probe amplification of all relevant exons of the MMR genes. Kaplan-Meier analysis of cumulative lifetime risk of breast cancer was made combining proven mutation carriers and their first-degree female relatives. RESULTS: After allocation of mutation status, the cumulative risk of breast cancer to 70 years in MLH1 carriers was 18.6% (95% CI 11.3 to 25.9)). This is significantly higher than the cumulative risk for MSH2 which was 11.2% (95% CI 1.4 to 21.0) to age 70 years (p=0.014). The UK population risk is 7.5%-8% at the age of 70 years. Prospective analysis identified six breast cancers in 1120 years of follow-up with an OR of 3.41 (95% CI 1.53 to 7.59). DISCUSSIONS: Female MLH1 carriers would appear to be at moderate risk of breast cancer and should be considered for breast screening at ages earlier than national screening programmes.

Cancer risk in Lynch Syndrome.

Lynch Syndrome, or hereditary non-polyposis colorectal cancer (HNPCC) is an autosomal dominant cancer predisposition syndrome caused by inactivating mutations in DNA mismatch repair genes. It accounts for 2-4 % of all incident colorectal cancers. Mutation carriers are at risk of early onset colorectal cancer, endometrial cancer, and a spectrum of other tumours. Accurate estimation of cancer risk for mutation carriers is essential for counselling, and establishing appropriate screening guidelines. This study reviews the current data on cancer risk, and emerging risk reduction strategies.

A comparative study of quantitative immunohistochemistry and quantum dot immunohistochemistry for mutation carrier identification in Lynch syndrome.

AIMS: Lynch Syndrome is caused by mutations in DNA mismatch repair (MMR) genes. Mutation carrier identification is facilitated by immunohistochemical detection of the MMR proteins MHL1 and MSH2 in tumour tissue and is desirable as colonoscopic screening reduces mortality. However, protein detection by conventional immunohistochemistry (IHC) is subjective, and quantitative techniques are required. Quantum dots (QDs) are novel fluorescent labels that enable quantitative multiplex staining. This study compared their use with quantitative 3,3'-diaminobenzidine (DAB) IHC for the diagnosis of Lynch Syndrome. METHODS: Tumour sections from 36 mutation carriers and six controls were obtained. These were stained with DAB on an automated platform using antibodies against MLH1 and MSH2. Multiplex QD immunofluorescent staining of the sections was performed using antibodies against MLH1, MSH2 and smooth muscle actin (SMA). Multispectral analysis of the slides was performed. The staining intensity of DAB and QDs was measured in multiple colonic crypts, and the mean intensity scores calculated. Receiver operating characteristic (ROC) curves of staining performance for the identification of mutation carriers were evaluated. RESULTS: For quantitative DAB IHC, the area under the MLH1 ROC curve was 0.872 (95% CI 0.763 to 0.981), and the area under the MSH2 ROC curve was 0.832 (95% CI 0.704 to 0.960). For quantitative QD IHC, the area under the MLH1 ROC curve was 0.812 (95% CI 0.681 to 0.943), and the area under the MSH2 ROC curve was 0.598 (95% CI 0.418 to 0.777). CONCLUSIONS: Despite the advantage of QD staining to enable several markers to be measured simultaneously, it is of lower utility than DAB IHC for the identification of MMR mutation carriers. Automated DAB IHC staining and quantitative slide analysis may enable high-throughput IHC.

Semiquantitative assessment of immunohistochemistry for mismatch repair proteins in Lynch syndrome.

AIMS: To assess semiquantitative immunohistochemistry as used in the diagnosis of Lynch syndrome. METHODS AND RESULTS: Tumour sections from 51 mutation carriers and 17 controls were stained with antibodies against MLH1, MSH2, MSH6 and PMS2. Intensity of immunoreactivity and percentage positivity were recorded on scales of 0-3 and 0-4, respectively. These scores were multiplied for a score of 0-12 per slide. Receiver-operator characteristic (ROC) curves of staining performance for the identification of mutation carriers were evaluated, and optimum cut-offs calculated. The area under the MLH1 ROC curve was 0.981 [95% confidence interval (CI) 0.952, 1.000]. The area under the MSH2 ROC curve was 0.899 (95% CI 0.796, 1.000). For MLH1 staining, a score