Lynch syndrome, characterized by DNA mismatch repair deficiency, represents a significant paradigm among cancer predisposition syndromes and is notably associated with heightened susceptibility to various cancers, particularly colorectal and endometrial malignancies. The primary aim of this research paper is to scrutinize specific associations and delve into the underlying molecular mechanisms of Lynch syndrome. Genetic alterations in MMR genes, including MLH1, MSH2, MSH6, PMS2, and EPCAM, compromise DNA repair mechanisms, predisposing affected individuals to a spectrum of malignancies. This paper comprehensively investigates current screening methodologies and preventive measures tailored for individuals identified or at risk of Lynch syndrome. The integration of advanced sequencing technologies and refined bioinformatics tools has significantly improved mutation detection accuracy, facilitating precise identification of mutation carriers and their at-risk relatives. Moreover, this review emphasizes the evolving diagnostic landscape, which have revolutionized the identification of potential mutation carriers. The structured diagnostic algorithm, incorporating clinical criteria, tumor testing, and genetic analysis, plays a pivotal role in systematically identifying and managing individuals with Lynch syndrome. While the well-established association of Lynch syndrome with colorectal and endometrial cancers is recognized, emerging evidence suggests an increased risk for other types of malignancies. A crucial aspect of this literature review is to extensively analyze the less commonly acknowledged correlation between Lynch syndrome and prostate or testicular malignancies. Understanding these correlations holds significant importance in guiding tailored screening protocols and preventive strategies for individuals carrying Lynch syndrome-associated genetic mutations. The comprehensive assessment of this diverse spectrum of cancers underscores the necessity for tailored surveillance strategies and multidisciplinary approaches to effectively manage and mitigate risks in individuals harboring Lynch syndrome-associated genetic alterations.

Myxofibrosarcoma is a malignant fibroblastic neoplasm that commonly arises in the extremities, with mediastinum being a very rare location. The development of sarcomas is uncommon in patients with Lynch syndrome. We present a Lynch syndrome patient with synchronous cecal adenocarcinoma and mediastinal myxofibrosarcoma with both harboring the same loss-of-function MSH2 alteration (c.2634 + 1G > A splice region variant). Metastatic myxofibrosarcoma in the left chest wall developed 6 months after the initial diagnosis. The clinical presentation, imaging findings, histopathology, and molecular studies along with differential diagnoses are presented and discussed.

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.

A subset of patients with Lynch Syndrome demonstrates cutaneous manifestations of the disorder. Characterization of these Lynch-related skin lesions could help in early recognition of patients with Lynch Syndrome. A broad search of the literature on OVID Medline and Embase was carried out to capture papers reporting cutaneous manifestations in Lynch Syndrome patients. The results were uploaded into Mendeley reference management software. The PRISMA workflow was used in the literature selection process. In this systematic review, data were collected from 961 cases from 413 studies, including 380 molecularly confirmed Lynch Syndrome cases. The main skin lesions were: Sebaceous adenomas (43%), sebaceous carcinomas (27%), keratoacanthomas (16%), sebaceomas (13%), squamous cell carcinomas (23%), and basal cell carcinomas (10%). MSH2 variants were the most common underlying genotype (72%). Assessment of mismatch repair by immunohistochemistry, microsatellite instability analysis, or both were performed on 328 skin lesions from 220 (58%) molecularly confirmed cases. In those skin lesions, 95% of Immunohistochemistry and 90% of the microsatellite instability test results were concordant with the underlying genotype. Sebaceous skin lesions are well-recognised phenotypic features of Lynch Syndrome. Our results show that squamous and basal cell carcinomas are relatively common in patients with Lynch syndrome; however, available evidence cannot confirm that Lynch syndrome is causal. Immunohistochemistry and/or microsatellite instability testing of skin tumours in patients with a family history of Lynch Syndrome-associated cancers may be a useful approach in identifying patients requiring referral to Clinical Genetics and/or consideration of germline genetic testing for Lynch Syndrome.

Reflex mismatch repair immunohistochemistry (MMR IHC) testing for MLH1, PMS2, MSH2 and MSH6 is used to screen for Lynch syndrome. Recently MMR-deficiency (MMRd) has been approved as a pan-cancer predictive biomarker for checkpoint inhibitor therapy, leading to a vast increase in the use of MMR IHC in clinical practice. We explored whether immunohistochemical staining with PMS2 and MSH6 can be used as a reliable substitute. This two-antibody testing algorithm has the benefit of saving tissue, cutting costs and saving time. PubMed, Embase and Cochrane library were systematically searched for articles reporting on MMR IHC. The weighed percentage of cases with isolated MLH1 or MSH2 loss or combined MLH1/MSH2 loss alone was analyzed using a random effects model meta-analysis in R. The search yielded 1704 unique citations, of which 131 studies were included, describing 9014 patients. A weighed percentage of 1.1% (95% CI 0.53-18.87, I = 87%) of cases with isolated MLH1 or MSH2 loss or combined MLH1/MSH2 loss alone was observed. In the six articles with the main aim of investigating the two-antibody testing algorithm all MMRd cases were detected with the two-antibody testing algorithm, there were no cases with isolated MLH1 or MSH2 loss or combined MLH1/MSH2 loss alone. This high detection rate of MMRd of the two-antibody testing algorithm supports its use in clinical practice by specialized pathologists. Staining of all four antibodies should remain the standard in cases with equivocal results of the two-antibody testing algorithm. Finally, educational sessions in which staining pattern pitfalls are discussed will continue to be important.

Microsatellite instability (MSI) is caused by defects in DNA mismatch repair (MMR) components. Inactivation of any MMR gene(s), including hMLH1, hMSH2, hMSH6, and hPMS2, can result in MSI. Immunohistochemistry (IHC) is a sensitive and specific screening tool for MSI that can detect loss of expression of one or more MMR components. Of the four MMR markers, hMLH1 and hMSH2 are considered most informative of MSI status. There has been renewed interest in MSI status in view of its favorable association with response to immune checkpoint inhibitors in some cancers. MMR expression patterns in acute myeloid leukemia (AML) have not been evaluated systematically.
We used clinically-validated IHC assays to assess the expression of hMLH1, hMSH2, hMSH6, and/or hPMS2 in formalin-fixed paraffin-embedded tissue sections of bone marrow core biopsies from patients diagnosed with AML. Mutation profiling was performed using next-generation sequencing to assess for mutations in MMR genes.
The study group included 236 patients with AML, including a cohort treated on a clinical trial of azacitidine and nivolumab (NCT02397720). In addition, hMSH6, and/or hPMS2 expression was assessed in 99 AML patients with diploid karyotype. All patients, except two, had retained expression of all MMR markers assessed: One patient from the azacytidine+nivolumab group had zonal patchy loss of staining of hMLH1 and, to a lesser extent, a similar staining pattern of hMSH2; and one patient from the AML with diploid karyotype group had loss of hMSH2 but retained expression of hMLH1, hMSH6 and hPMS2. In addition, a retrospective analysis on a separate cohort of 139 patients with primary AML, on which next generation sequencing profiling was performed, identified 14 cases with alterations in MMR genes.
MMR loss is a rare event in AML, thus does not appear to underlie response patterns to anti-PD1 therapy.

UNASSIGNED: Lynch Syndrome (LS) is a cancer-predisposing condition resulting from hereditary mutation of DNA mismatch repair genes. Gastrointestinal, urogenital, and endometrial carcinomas are well-known to predominantly occur in LS patients. In contrast, there are only few reports on brain tumours in the context of LS and to date intracranial tumour manifestation appear to be rather coincidental.
UNASSIGNED: We present the case of a 56-year-old female developing aggressive lactotroph pituitary adenoma following a history of multiple Lynch-associated malignomas and having a confirmed MSH2 mutation. Furthermore, we performed a literature review via PubMed using the search terms \'Lynch Syndrome\', \'HNPCC\', \'MMR mutation\' combined with \'intracranial tumour\', \'sellar tumour\', \'pituitary adenoma\', or \'pituitary carcinoma\', focusing on other reported cases and treatment regimens.
UNASSIGNED: A handful of studies have indicated an increased frequency of brain tumours in the context of LS, predominantly glioblastoma and less frequently low-grade glioma or other brain tumours. Based on our literature review, we summarized the known instances of pituitary adenoma in LS patients, including the present case. Furthermore, we reviewed the common recommendation of using temozolomide (TMZ) for treatment of aggressive pituitary adenoma or carcinoma and found strong indication that it might be insufficient in LS patients, while PD-1 blockade could be a promising treatment option.
UNASSIGNED: Combined with our case, there is a growing body of evidence that intracranial tumours and in particular those of the sellar region might be more prevalent in LS patients than previously assumed, due to their genetic profile substantially affecting viability and efficacy of treatment options. Clinical signs of aggressive tumour growth in combination with irresponsiveness to standard treatment in case of recurrence should lead to further diagnostic measures, because revelation of germline MMR mutations would call for an extended screening for other neoplastic manifestations and would markedly influence further treatment.

Colorectal cancer (CRC) represents a major malignancy globally, with microsatellite instability as its second top molecular mechanism of carcinogenesis. Immunohistochemical (IHC), whose sensitivity and specificity exceed 90%, is used routinely to detect 4 MMR proteins (MLH1, PMS2, MSH2, and MSH6) for screening mismatch repair system defects. We aimed to assess associations of clinicopathologic characteristics with MMR status in resectable CRC patients.Stage I-III CRC cases administered surgical resection in Zhejiang Cancer Hospital in 2013 to 2015 were retrospectively analyzed. MLH1, MSH2, MSH6, and PMS2 protein amounts were evaluated immunohistochemically. Clinicopathological information, including age, sex, tumor location, histological subclass, disease stage, regional lymph node (LN) metastasis, American Joint Committee on Cancer (AJCC) 8th edition stage, and survival data were retrospectively reviewed.A total of 133 CRC cases were assessed, including 74 (55.6%), 45 (33.8%), 55 (41.4%), and 77 (57.9%) not expressing MLH1, MSH2, MSH6, and PMS2, respectively. There were significant associations of MLH1, MSH2, MSH6, and PMS2 proteins with age and sex (P < .05). MLH1, MSH2, and MSH6 (but not PMS2) showed positive associations with primary tumor location (P < .05). Of the 133 patients, 70 and 63 cases were affected on the right and left sides, respectively; significant associations of primary site with age and sex were observed (P < .05). Regarding the MMR status, MLH1, MSH2, and MSH6 protein expression levels were positively associated with primary site (P < .05). Five-year overall survival (OS) rates were 84.2% and 79.2% in left-side and right-side cases, respectively; 5-year disease-free survival (DFS) rates were 74.0% and 69.8%, respectively. Survival had no differences between left- and right-side patients in terms of OS (P = .318) and DFS (P = .481).These data demonstrate that 4 major dMMR proteins are expressed differently in left- and right-side CRCs, and survival is comparable in right- and left-side resectable CRC cases with dMMR.

Muir-Torre syndrome is a rare subtype of Lynch syndrome characterized by coincidence of skin neoplasm and visceral malignancies. Here, we report a case of this rare disease, whose diagnosis of the syndrome was first suspected by the pathologist. This was a 60-yr-old woman who presented with an axillary skin nodule, which was diagnosed as basal cell carcinoma. Further inquiry revealed that she was hospitalized for evaluation of a recurrent vaginal stump endometrial carcinoma. Histologic workup and immunohistochemistry for mismatch repair proteins of both the skin and vaginal tumor suggested the possibility of Muir-Torre syndrome. NexGen sequencing identified a frame-shift mutation in the MSH2 gene. The patient was found to have a metachronous colorectal carcinoma, uterine endometrial carcinoma, and skin cancer from 1998 to 2016. Five family members had also suffered from colorectal cancer or glioma. This case report illustrates the importance of the multidisciplinary care approach, mismatch repair protein and gene testing, and detailed medical history taking into consideration the diagnosis of Muir-Torre syndrome.

Among the types of cancers that may occur in the oral cavity, squamous cell carcinomas (SCC) of the mouth have a higher incidence and are associated with increased rates of morbidity and mortality. Among steps from the beginning to the progression of the tumour, DNA Repair System is highlighted. The present study aims to conduct a systematic review of the literature on the expression of the repair genes hMSH2 and hMSH6 in patients with SCC in the mouth and oropharyngeal region. The search was performed in databases such as PubMed, Lilacs, and Scielo and included articles published in English from 1999 until 2015. The search in the above-mentioned databases initially yielded 15 scientific articles related to the proposed objective. After a detailed analysis of each of them, only 8 were included in the present review, precisely because they met the inclusion criteria determined in the method. All the reviewed works were unanimous in recognizing the veracity and complexity of the Genomic Repair System, also called Mismatch Repair System, confirming the participation of repair gene proteins (such as hMSH2 and hMSH6) in patients with oral cancer and even of lesions that are susceptible to malignization. SIGNIFICANCE OF THE STUDY: Worldwide, there are an estimated 300 thousand new cases of oral cancer per year. Studies have shown a greater risk in individuals who are smokers and alcohol consumers in developing mouth cancer. Many steps are observed from the beginning to the progression of the tumour, highlighted among them is the moment in which genetic, and epigenetic alterations will interfere in the functioning of the DNA Repair System. This work presents a survey of current knowledge about the involvement of repair genes, especially those of the MutSα system, in the development and progression of oral cancer.