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The Prospective Lynch Syndrome Database (PLSD) has been developed as an international, multicentre, prospective, observational study that aims to provide age and organ-specific cancer risks according to gene and gender, estimates of survival after cancer and information on the effects of interventions. Recent reports from PLSD provided improved estimates of cancer risks and survival and showed that different time intervals between surveillance colonoscopies did not affect the incidence, stage or prognosis of colorectal cancer. The PLSD reports suggest that current management guidelines for Lynch syndrome should be revised in light of the different gene and gender-specific cancer risks and the good prognosis for the most commonly associated cancers. In this review, we describe the discrepancies between the current management guidelines for Lynch Syndrome and the most recent prospective observational studies, indicating the areas of further research. Keywords Lynch syndrome · Hereditary non-polyposis colorectal cancer · Colorectal cancer · Colonoscopy · Surveillance · Prevention · Precision medicine · PLSD · Cancer incidence

Germline pathogenic variants in the DNA mismatch repair genes (MMR): MLH1, MSH2, MSH6, and PMS2, are causative of Lynch syndrome (LS). However, many of the variants mapping outside the invariant splice site positions (IVS ± 1, IVS ± 2) are classified as variants of unknown significance (VUS). Three such variants (MLH1 c.588+5G>C, c.588+5G>T and c.677+5G>A) were identified in 8 unrelated LS families from Argentina, Brazil and Chile. Herein, we collected clinical information on these families and performed segregation analysis and RNA splicing studies to assess the implication of these VUS in LS etiology. Pedigrees showed a clear pattern of variant co-segregation with colorectal cancer and/or other LS-associated malignancies. Tumors presented deficient expression of MLH1-PMS2 proteins in 7/7 of the LS families, and MSI-high status in 3/3 cases. Moreover, RNA analyses revealed that c.588+5G>C and c.588+5G>T induce skipping of exon 7 whereas c.677+5G>A causes skipping of exon 8. In sum, we report that the combined clinical findings in the families and the molecular studies provided the evidences needed to demonstrate that the three MLH1 variants are causative of LS and to classify c.588+5G>C and c.677+5G>A as class 5 (pathogenic), and c.588+5G>T as class 4 (likely-pathogenic). Our findings underline the importance of performing clinical and family analyses, as well as RNA splicing assays in order to determine the clinical significance of intronic variants, and contribute to the genetic counseling and clinical management of patients and their relatives.

Microsatellite instability (MSI) is a hallmark tool for Lynch syndrome (LS) screening and a prognostic marker for sporadic colorectal cancer (CRC). In regions with limited resources and scarce CRC molecular characterization as South America, the implementation of universal MSI screening is under debate for both its purposes. We sought to estimate the frequency of BAT26 in colorectal adenocarcinomas and to determine associated clinical and histological features. Consecutive patients from a CRC registry were included. BAT26 determination was performed in all cases; if instability was found, immunohistochemistry (IHC) and BRAF mutation analyses were done, as appropriate. Differences were assessed by chi-squared or Fisher’s exact test, or by T test or Mann–Whitney. Multiple logistic regression was used to identify factors independently associated with BAT26-unstable tumors. We included 155 patients; mean age was 65.6 (SD 14.4) and 56.1% were male. The frequency of BAT26-unstable tumors was 22% (95% CI 15.7–29.3). Factors independently associated with BAT26-unstable tumors were right colon localization (OR 3.4, 95% CI 1.3–8.7), histological MSI features (OR 5.1, 95% CI 1.9–13.6) and Amsterdam criteria (OR 23.2, 95% CI 1.9–286.7). IHC was altered in 85.3% BAT26-unstable tumors and 70.6% lacked MLH1 expression; 47.8% of these harbored BRAF V600E mutation. We provide evidence to link the frequency of BAT26 to an increased diagnostic yield (up to 1.4-folds) of suspected LS cases in comparison to the revised Bethesda guidelines alone. In regions with limited resources, clinical and histological features associated with BAT26-unstable status could be useful to direct MSI screening in sporadic CRCs and may help guide clinical care and future research. Fil: González, María Laura. Hospital Italiano; Argentina Fil: Causada Calo, Natalia. Hospital Italiano; Argentina. McMaster University; Canadá Fil: Santino, Juan Pablo. Hospital Italiano; Argentina Fil: Dominguez Valentin, Mev. The Norwegian Radium Hospital; Noruega Fil: Ferro, Fabiana Alejandra. Hospital Italiano; Argentina Fil: Sammartino, Inés. Hospital Italiano; Argentina Fil: Kalfayan, Pablo Germán. Hospital Italiano; Argentina Fil: Verzura, Maria Alicia. Hospital Italiano; Argentina Fil: Piñero, Tamara Lejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Hospital Italiano; Argentina Fil: Cajal, Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Hospital Italiano; Argentina Fil: Pavicic, Walter Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Hospital Italiano; Argentina Fil: Vaccaro, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Hospital Italiano; Argentina

To study the potential contribution of genes other than BRCA1/2, PTEN, and TP53 to the biological and clinical characteristics of multiple early-onset cancers in Norwegian families, including early-onset breast cancer, Cowden-like and Li-Fraumeni-like syndromes (BC, CSL and LFL, respectively). The Hereditary Cancer Biobank from the Norwegian Radium Hospital was used to identify early-onset BC, CSL or LFL for whom no pathogenic variants in BRCA1/2, PTEN, or TP53 had been found in routine diagnostic DNA sequencing. Forty-four cancer susceptibility genes were selected and analyzed by our in-house designed TruSeq amplicon-based assay for targeted sequencing. Protein- and RNA splicing-dedicated in silico analyses were performed for all variants of unknown significance (VUS). Variants predicted as the more likely to affect splicing were experimentally analyzed by minigene assay. We identified a CSL individual carrying a variant in CHEK2 (c.319+2T>A, IVS2), here considered as likely pathogenic. Out of the five VUS (BRCA2, CDH1, CHEK2, MAP3K1, NOTCH3) tested in the minigene splicing assay, only NOTCH3 c.14090C>T (p.Ser497Leu) showed a significant effect on RNA splicing, notably by inducing partial skipping of exon 9. Among 13 early-onset BC, CSL and LFL patients, gene panel sequencing identified a potentially pathogenic variant in CHEK2 that affects a canonical RNA splicing signal. Our study provides new information on genetic loci that may affect the risk of developing cancer in these patients and their families, demonstrating that genes presently not routinely tested in molecular diagnostic settings may be important for capturing cancer predisposition in these families.

Lynch syndrome (LS) is an autosomal dominant syndrome that predisposes individuals to development of cancers early in life. These cancers are mainly the following: colorectal, endometrial, ovarian, small intestine, stomach and urinary tract cancers. LS is caused by germline mutations in DNA mismatch repair genes (MMR), mostly MLH1 and MSH2, which are responsible for more than 85% of known germline mutations. To search for germline mutations in MLH1 and MSH2 genes in 123 unrelated South American suspected LS patients (Bethesda or Amsterdam Criteria) DNA was obtained from peripheral blood, and PCR was performed followed by direct sequencing in both directions of all exons and intron-exon junctions regions of the MLH1 and MSH2 genes. MLH1 or MSH2 pathogenic mutations were found in 28.45% (34/123) of the individuals, where 25/57 (43.85%) fulfilled Amsterdam I, II and 9/66 (13.63%) the Bethesda criteria. The mutations found in both genes were as follows: nonsense (35.3%), frameshift (26.47%), splicing (23.52%), and missense (9%). Thirteen alterations (35.14%) were described for the first time. The data reported in this study add new information about MLH1 and MSH2 gene mutations and contribute to better characterize LS in Brazil, Uruguay and Argentina. The high rate of novel mutations demonstrates the importance of defining MLH1 and MSH2 mutations in distinct LS populations.

Lynch syndrome (LS) is caused by inherited germline mutations in mismatch repair (MMR) genes. It is one of the commonest forms of inherited predisposition to colorectal cancer (CRC), accounting for 2-5% of all CRC. LS is characterized by early age of onset, with a tendency for multiplicity and an increased risk for extra-colonic tumors at particular sites. In this study we have evaluated the frequency of extra-colonic tumors in 60 unrelated LS families fulfilling the Amsterdam criteria (ACI. ACII) from the Oncotree database of the Hereditary Colorectal Cancer Registry of the AC Camargo Hospital. All families' pedigree was extensively analyzed, varying from 2 to 6 generations with a total of 2,095 individuals evaluated. As expected, colorectal cancer was the most frequent tumor in the families (334 cases). We found 200 extracolonic tumors among all individuals with a higher ratio in women (123 cases) than men (77 cases). By far, breast cancer (32 cases) was the most frequent extracolonic manifestation in women followed by endometrial (20 cases) and uterine cervix cancer (20 cases). For man, prostate (16 cases) and stomach (12 cases) cancer were the most frequent extracolonic tumors. It is well know that establishing the diagnosis is challenging and requires knowledge and surveillance. Thus, recognition of individuals and families with hereditary predisposition to cancer according to clinical and molecular features, combined with intensive surveillance and management programs, can contribute substantially to improve results related to the diagnosis and characterization of LS.