Real-world uptake of Lynch syndrome testing among patients with mismatch repair-deficient endometrial cancer in Québec.

There is lack of data pertaining to Lynch syndrome presenting as endometrial cancer in Quebec. We evaluated real-world follow-up of mismatch repair-deficient (dMMR) endometrial cancers screened through universal immunohistochemistry at a tertiary center in Québec. Among 222 dMMR tumors, MLH1/PMS2 loss predominated. Seventy-four patients with methylation-negative tumors were eligible for Lynch syndrome evaluation; 73 (98.6%) were referred, and 57 completed germline testing. Pathogenic germline variants were identified in 54.4%. These findings demonstrate high downstream testing uptake and a substantial diagnostic yield, underscoring the importance of systematic linkage from tumor screening to genetic assessment to optimize Lynch syndrome detection.