It is estimated that 153,020 cases of CRC per year, with an increase in diagnoses in younger patients. We present a case of a female with an early presentation of Lynch Syndrome and CRC, who, on her third malignant presentation, was re-diagnosed as a constitutional mismatch repair deficiency.

Current algorithms for diagnosing Lynch syndrome (LS) include multistep molecular tumor tests to distinguish LS-associated from sporadic colorectal cancer (CRC), which add cost and complexity to the evaluation. We hypothesized that PREMM5, a clinical LS prediction tool, could be an alternative approach to screen for LS, thereby lessening the need for specialized molecular diagnostics. We reviewed a consecutively ascertained institutional cohort of 1058 CRC patients on whom pathologic and clinical data were available, including prior LS germline testing. Data from MMR-D/MSI-H CRC patients were reviewed and PREMM5 scores were calculated for each individual. Using a PREMM5 score cutoff ≥ 2.5% to characterize the need for germline testing, we determined the rate of pathogenic/likely pathogenic germline variants (PGVs) in LS genes in patients with PREMM5 scores ≥ 2.5% versus < 2.5%. Sensitivity and negative predictive values (NPV) of PREMM5 were calculated for all MMR-D/MSI-H CRC patients, and those with MLH1-deficient CRC. MMR IHC and/or MSI results were available on 572/1058 cases. We identified 74/572 (12.9%) cases as MMR-D/MSI-H, of which 28/74 (37.8%) harbored a LS PGV. 11/49 (22.4%) patients with MLH1-deficient CRC harbored a LS PGV. PREMM5 had 100% sensitivity (95% CI: 87.7-100 for any MMR-D/MSI-H; 95% CI: 71.5-100 for MLH1-deficient CRC) and 100% NPV (95% CI: 83.2-100 for any MMR-D/MSI-H; 95% CI: 82.4-100 for MLH1-deficient CRC) for identifying LS PGVs in these cohorts. PREMM5 accurately distinguishes LS- from non-LS-associated MMR-D/MSI-H CRC without additional somatic molecular testing. These findings are particularly relevant for limited-resource settings where advanced molecular diagnostics may be unavailable.

Lynch syndrome (LS), also known as Hereditary Non-Polyposis Colorectal Cancer (HNPCC), is an autosomal dominant cancer syndrome which causes about 2-3% of cases of colorectal carcinoma. The development of LS is due to the genetic and epigenetic inactivation of genes involved in the DNA mismatch repair (MMR) system, causing an epiphenomenon known as microsatellite instability (MSI). Despite the fact that the genetics of the vast majority of MSI-positive (MSI+) cancers can be explained, the etiology of this specific subset is still poorly understood. As a possible new mechanism, it has been recently demonstrated that the overexpression of certain microRNAs (miRNAs, miRs), such as miR-155, miR-21, miR-137, can induce MSI or modulate the expression of the genes involved in LS pathogenesis. MiRNAs are small RNA molecules that regulate gene expression at the post-transcriptional level by playing a critical role in the modulation of key oncogenic pathways. Increasing evidence of the link between MSI and miRNAs in LS prompted a deeper investigation into the miRNome involved in these diseases. In this regard, in this study, we discuss the emerging role of miRNAs as crucial players in the onset and progression of LS as well as their potential use as disease biomarkers and therapeutic targets in the current view of precision medicine.

OBJECTIVE: The role of small-bowel (SB) cancer surveillance by capsule endoscopy (CE) in Lynch syndrome (LS) patients has been investigated in recent years, with contradicting results. This meta-analysis evaluates the diagnostic yield (DY) of CE as a screening tool in asymptomatic LS patients.
METHODS: A systematic literature search was performed for all studies reporting the results of SB cancer screening in patients with LS. The primary outcome was the evaluation of the DY of CE in this setting for consecutive screening rounds.
RESULTS: Five studies comprising 428 patients and CE 677 procedures were included for data extraction and statistical analysis. The estimated pooled DY for CE-identified pathological findings was 8% in the first screening round and 6% in the second. Limiting the analysis to histologically-confirmed pathological findings, the pooled DY of second-round screening dropped to 0%. The included studies showed a significantly different prevalence of pathogenic variants in mismatch repair (path_MMR) genes, which underlie different cumulative incidences of extracolonic cancers.
CONCLUSIONS: SB surveillance by CE with a 2-year interval in asymptomatic LS individuals does not appear to be an effective screening strategy. Confirmatory prospective studies in this context are needed, considering the different cumulative incidence of SB tumors according to underlying path_MMR defects.

Visceral malignancies in patients with Lynch syndrome behave less aggressively than in those without Lynch syndrome. The behavior of sebaceous carcinoma (SC) in Muir-Torre syndrome (MTS), a variant of Lynch syndrome, is incompletely investigated.
To investigate features and survival of SC patients with and without MTS.
Retrospective cohort study in the Surveillance, Epidemiology, and End Results 17 database from 2000 to 2019 of patients with SC. Patients were classified as MTS or non-MTS cases based on a threshold score of 2 on the Mayo MTS risk score.
We identified 105 (2.8%) MTS cases and 3677 (97.2%) non-MTS cases. On univariate analysis, MTS patients were younger, had a higher proportion of tumors outside the head/neck, and had fewer high-grade tumors. On Kaplan-Meier analysis, MTS patients trended toward having better SC-specific survival. On multivariate Cox proportional hazards analysis adjusting for other covariates, MTS status was an independent predictor of worse overall survival. However, there was no association between MTS status and SC-specific survival.
Given relatively high disease-specific survival in SC, our study may have been underpowered to detect a difference on Kaplan-Meier analysis.
Our study suggests SC does not behave more aggressively in patients with MTS.

OBJECTIVE: Lynch syndrome (LS) is the secondary cause of hereditary ovarian cancer (OC). Germline mutations in the DNA-mismatch repair (MMR) genes cause tumorigenesis and a high immunogenicity. Recent studies showed a promising use of immunotherapy in MMR deficient (MMRd) tumors. This is a case report of a patient with LS-associated OC and a complete response to pembrolizumab.
METHODS: A 44-year-old patient was admitted to the hospital with lower abdominal pain. The patient\'s history showed LS with a germline mutation in the MSH2-gene. Initial diagnostics showed a pelvic tumor mass and a highly elevated cancer antigen 125. After debulking surgery, histopathological findings showed a high-grade serous OC with mutations in the MSH2 and MSH6 genes. Only 5 weeks after operation with no residual tumor mass, a quick and significant intraabdominal progression of the disease was diagnosed. Adjuvant therapy with carboplatin and paclitaxel in a weekly course did not lead to sustainable response. An anti-PD-L1 antibody therapy with pembrolizumab was initiated. After only two courses of therapy, the laboratory results and clinical status of the patient improved tremendously. Shortly after, a complete response was detected, and therapy is still ongoing. The patient remains tumor free for 21 months now.
CONCLUSIONS: The significance of germline compared to somatic mutations has not yet been sufficiently investigated. To our knowledge, this is the first case with complete response to checkpoint inhibition in OC associated with LS. Regarding LS-associated OC, immune checkpoint inhibition is an efficient therapy in tumors nonresponsive to standard therapy.

Little is known about patient-specific risk factors for skin neoplasia in individuals with Lynch syndrome (LS).
Identify clinical factors associated with development of skin neoplasms in LS.
Clinical data were systematically collected on a cohort of LS carriers (confirmed pathogenic germline variants in MLH1, MSH2, MSH6, PMS2, or EPCAM) age ≥18 undergoing clinical genetics care at Dana-Farber Cancer Institute from January 2000 to March 2020. Multivariable logistic regression was performed to evaluate clinical factors associated with skin neoplasia.
Of 607 LS carriers, 9.2% had LS-associated skin neoplasia and 15.0% had non-LS-associated skin neoplasia; 58.2% (353/607) had documentation of prior dermatologic evaluation; 29.7% (38/128) with skin neoplasms lacked a history of visceral LS-associated malignancy. LS-associated skin neoplasms were significantly associated with male sex, age, race, MLH1 pathogenic germline variants, MSH2/EPCAM pathogenic germline variants, and personal history of non-LS skin neoplasms. Non-LS-associated skin neoplasms was significantly associated with age, number of first- and second-degree relatives with non-LS-associated skin neoplasms, and personal history of LS-associated skin neoplasms.
Single-institution observational study; demographic homogeneity.
Skin neoplasms are common in individuals with LS. We identified clinical factors associated with LS- and non-LS-associated skin neoplasms. Regular dermatologic surveillance should be considered for all LS carriers.

Lynch syndrome is one of the most common cancer predisposition syndromes. It is caused by inherited changes in the mismatch repair pathway. With current diagnostic approaches, a causative genetic variant can be found in less than 50% of cases. A correct diagnosis is important for ensuring that an appropriate surveillance program is used and that additional high-risk family members are identified.
We used clinical genome sequencing on DNA from blood and subsequent transcriptome sequencing for confirmation. Data were analyzed using the megSAP pipeline and classified according to basic criteria in diagnostic laboratories. Segregation analyses in family members were conducted via breakpoint PCR.
We present a family with the clinical diagnosis of Lynch syndrome in which standard diagnostic tests, such as panel or exome sequencing, were unable to detect the underlying genetic variant. Genome sequencing in the index patient confirmed the previous diagnostic results and identified an additional complex rearrangement with intronic breakpoints involving MLH1 and its neighboring gene LRRFIP2. The previously undetected structural variant was classified as medically relevant. Segregation analysis in the family identified additional at-risk individuals which were offered intensified cancer screening.
This case illustrates the advantages of clinical genome sequencing in detecting structural variants compared with current diagnostic approaches. Although structural variants are rare in Lynch syndrome families, they seem to be underreported, in part because of technical challenges. Clinical genome sequencing offers a comprehensive genetic characterization detecting a wide range of genetic variants.

Cancer is one of the most common causes of death worldwide. A strong predisposition to cancer is generally only observed in colorectal cancer (5% of cases) and breast cancer (2% of cases). Colorectal cancer is the most common cancer with a strong genetic predisposition, but it includes dozens of various syndromes. This group includes familial adenomatous polyposis, attenuated familial adenomatous polyposis, MUTYH-associated polyposis, NTHL1-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis syndrome, Cowden syndrome, Lynch syndrome, and Muir-Torre syndrome. The common symptom of all these diseases is a very high risk of colorectal cancer, but depending on the condition, their course is different in terms of age and range of cancer occurrence. The rate of cancer development is determined by its conditioning genes, too. Hereditary predispositions to cancer of the intestine are a group of symptoms of heterogeneous diseases, and their proper diagnosis is crucial for the appropriate management of patients and their successful treatment. Mutations of specific genes cause strong colorectal cancer predispositions. Identifying mutations of predisposing genes will support proper diagnosis and application of appropriate screening programs to avoid malignant neoplasm.

OBJECTIVE: Lynch Syndrome (LS) individuals have a 25-75% lifetime risk of developing colorectal cancer. Colonoscopy screening decreases this risk. This study compared the cost of Strategy 1: screening colonoscopy for 1st degree relatives of patients that met the Revised Bethesda Criteria (i.e., probands) to Strategy 2: screening colonoscopy for 1st degree relatives of probands with genetic mutations for Lynch Syndrome based in a resource-constrained health care system.
METHODS: A comparative, health care provider perspective, cost analysis was conducted at a tertiary hospital, using a micro-costing, ingredient approach. Forty probands that underwent genetic testing between November 01, 2014 and October 30, 2015 and their first-degree relatives were costed according to Strategy 1 and Strategy 2. Unit costs of colonoscopy and genetic testing were estimated and used to calculate and compare the total costs per strategy in South African rand (R) converted to UK pounds (£). Sensitivity analyses were performed on colonoscopy adherence, relatives\' positivity, and variable discount rates.
RESULTS: The cost for Strategy 1 amounted to £653 344/R6 161 035 compared to £49 327/R 465 155 for Strategy 2 (Discount rate 3%; Adherence 75%; and Positivity rate of relatives 45%). Base case analysis indicated a difference of 92% less in the total cost for Strategy 2 compared to Strategy 1. Sensitivity analyses showed that the difference in cost between the two strategies was not sensitive to variations in adherence, positivity or discount rates.
CONCLUSIONS: Colonoscopy screening for LS and at-risk family members was tenfold less costly when combined with genetic analysis. The logistics of rolling out this strategy nationally should be investigated.