Hereditary endometrial carcinoma is associated with germline mutations in Lynch syndrome genes. The role of other cancer predisposition genes is unclear. We aimed to determine the prevalence of cancer predisposition gene mutations in an unselected endometrial carcinoma patient cohort. Mutations in 25 genes were identified using a next generation sequencing based panel applied in 381 endometrial carcinoma patients who had undergone tumor testing to screen for Lynch syndrome. Thirty five patients (9.2%) had a deleterious mutation: 22 (5.8%) in Lynch syndrome genes (3 MLH1, 5 MSH2, 2 EPCAM-MSH2, 6 MSH6, 6 PMS2) and 13 (3.4%) in 10 non-Lynch syndrome genes (4 CHEK2, 1 each in APC, ATM, BARD1, BRCA1, BRCA2, BRIP1, NBN, PTEN, RAD51C). Of 21 patients with deleterious mutations in Lynch syndrome genes with tumor testing, 2 (9.5%) had tumor testing results suggestive of sporadic cancer. Of 12 patients with deleterious mutations in MSH6 and PMS2, 10 were diagnosed at age >50 and 8 did not have a family history of Lynch syndrome associated cancers. Patients with deleterious mutations in non-Lynch syndrome genes were more likely to have serous tumor histology (23.1% v 6.4%, p=0.02). The 3 patients with non-Lynch syndrome deleterious mutations and serous histology had mutations in BRCA2, BRIP1, and RAD51C. Current clinical criteria fail to identify a portion of actionable mutations in Lynch syndrome and other hereditary cancer syndromes. Performance characteristics of tumor testing are sufficiently robust to implement universal tumor testing to identify patients with Lynch syndrome. Germline multi-gene panel testing is feasible and informative, leading to the identification of additional actionable mutations.

Objective Determine factors impacting the uptake of genetic counseling and results of genetic testing following universal tumor testing for Lynch syndrome in patients with endometrial cancer. Methods The study population consisted of two unselected cohorts of endometrial cancer patients, 408 identified retrospectively and 206 identified prospectively. Immunohistochemistry for mismatch repair protein expression and/or microsatellite instability analysis was performed on these tumors. MLH1 methylation analysis was performed on tumors with loss of MLH1 protein. Tumor studies were considered suggestive of Lynch Syndrome if they showed immunohistochemical loss of MSH2, MSH6, or PMS2, loss of MLH1 without MLH1 promoter methylation, and/or microsatellite instability. Participants with suggestive tumor studies were contacted and offered genetic counseling and testing. Results In the retrospective cohort, 11% had tumor studies suggestive of Lynch syndrome. 42% were seen for genetic counseling. A germline mutation was detected in 40%, and one had a variant of uncertain significance. In the prospective cohort, 8.7% of patients had tumor testing suggestive of Lynch syndrome. 72% were seen for genetic counseling. Germline mutations were found in 40%, and one had a variant of uncertain significance. Common challenges included timing of re-contact, age, perceived lack of relevance, inability to travel, and limited insurance coverage. Conclusions There are several barriers to genetic counseling and testing follow up after universal tumor testing, and uninformative genetic test results present a management challenge. It is important to consider these limitations when implementing an approach to screening endometrial cancer patients for Lynch syndrome.

Clinical criteria, primarily young age of cancer onset and family history of signature cancers, have been developed to identify individuals at elevated risk for Lynch Syndrome with the goals of early identification and cancer prevention. In 2007, the Society of Gynecologic Oncology (SGO) codified criteria for women presenting with gynecologic cancers. These criteria have not been validated in a population-based setting. For 412 unselected endometrial cancers, immunohistochemical expression of DNA mismatch repair proteins and MLH1 methylation were assessed to classify tumors as sporadic or probable Lynch Syndrome. In this cohort, 10.5% of patients were designated as probable Lynch Syndrome based on tumor testing. The sensitivity and specificity of SGO criteria to identify these same cases were 32.6% (95% CI 19.2–48.5) and 77% (95% CI 72.7–81.8), respectively. With the exception of tumor location in the lower uterine segment, multivariate analysis of clinical features, family history, and pathologic variables failed to identify significant differences between the sporadic and probable Lynch Syndrome groups. A simplified cost-effectiveness analysis demonstrated that SGO clinical criteria and universal tissue testing strategies had comparable costs per probable Lynch Syndrome patient identified. In conclusion, SGO criteria successfully identify probable Lynch Syndrome cases among women with endometrial cancer who are young or have significant family history of signature tumors. However, a larger proportion of probable Lynch Syndrome patients who are older and have less significant family history are not detected by this screening strategy. Universal tissue testing may be necessary to capture more individuals at risk for having Lynch Syndrome.

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Clinical screening criteria, such as young age of endometrial cancer diagnosis and family history of signature cancers, have traditionally been used to identify women with Lynch Syndrome, which is caused by mutation of a DNA mismatch repair gene. Immunohistochemistry and microsatellite instability analysis have evolved as important screening tools to evaluate endometrial cancer patients for Lynch Syndrome. A complicating factor is that 15-20% of sporadic endometrial cancers have immunohistochemical loss of the DNA mismatch repair protein MLH1 and high levels of microsatellite instability due to methylation of MLH1. The PCR-based MLH1 methylation assay potentially resolves this issue, yet many clinical laboratories do not perform this assay. The objective of this study was to determine if clinical and pathologic features help to distinguish sporadic endometrial carcinomas with MLH1 loss secondary to MLH1 methylation from Lynch Syndrome-associated endometrial carcinomas with MLH1 loss and absence of MLH1 methylation. Of 337 endometrial carcinomas examined, 54 had immunohistochemical loss of MLH1. 40/54 had MLH1 methylation and were designated as sporadic, while 14/54 lacked MLH1 methylation and were designated as Lynch Syndrome. Diabetes and deep myometrial invasion were associated with Lynch Syndrome; no other clinical or pathological variable distinguished the 2 groups. Combining Society of Gynecologic Oncology screening criteria with these 2 features accurately captured all Lynch Syndrome cases, but with low specificity. In summary, no single clinical/pathologic feature or screening criteria tool accurately identified all Lynch Syndrome-associated endometrial carcinomas, highlighting the importance of the MLH1 methylation assay in the clinical evaluation of these patients.