Objective Lynch syndrome is a risk factor for developing endometrial carcinoma. Our aim was to evaluate the impact of gene-specific germline pathogenic variants on clinical features of patients affected by endometrial cancer.

Methods Patients with a diagnosis of endometrial cancer and with a germline pathogenic variant in mismatch repair genes were reviewed. Patients were classified on the basis of classes of risk according to the ESGO-ESGO-ESTRO (European Society of Medical Oncology/European Society of Gynaecological Oncology/European Society for Radiotherapy and Oncology) guidelines. One-way analysis of variance (ANOVA) and Kruskal-Wallis test were performed to compare three groups of continuous parametric and non-parametric variables, respectively. χ² test was used to analyze proportions.

Results Overall, 68 patients with endometrial cancer and Lynch syndrome were evaluated. Ten (14.7%) patients were excluded because of absence of information about the gene involved in Lynch syndrome, thus leaving 58 (85.3%) patients available for the final analysis. MLH1, MSH2, and MSH6 pathogenic variants were observed in 19 (32.7%), 33 (56.9%), and six (10.3%) patients, respectively. Mean±SD age at endometrial cancer diagnosis was 51±6.4, 43.5±7.4, and 60.3±8.8 years (p=0.0002). Prevalence of non-endometrioid endometrial cancer was 15.7%, 24.2%, and 0% in the MLH1, MSH2, and MSH6 groups, respectively (p=0.345). According to the ESMO-ESGO-ESTRO classification, low, intermediate, and high risk endometrial cancer accounted for 47.3%, 10.5%, and 42.1% of the MLH1 group, 57.6%, 3%, and 39.4% of the MSH2 group, and 50%, 50%m and 0% of the MSH6 group (p=0.009).

Conclusions Patients with MLH1 and MSH2 pathogenic variants are at a higher risk of early onset of endometrial cancer than patients with MSH6 pathogenic variants.