Current guidelines stratify patients with Lynch syndrome (LS) for colorectal cancer (CRC) risk and recommend colonoscopy frequency based on age and DNA mismatch repair genes with pathogenic variants. Despite following these guidelines, many patients are diagnosed with CRC after colonoscopy (i.e., postcolonoscopy CRC [PCRC]). Studying LS precancerous polyp risk rather than CRC risk could lead to more effective CRC prevention.

This prospective cohort study analyzed data from patients with LS undergoing colonoscopy at Mayo Clinic from March 22, 2002, to June 20, 2025.

The study included data from 143 patients with LS who underwent 557 colonoscopies. Two patients were diagnosed with CRC at their initial colonoscopy; however, no patients were diagnosed with PCRC at a subsequent colonoscopy. Precancerous polyp detection rates were 37.9% for adenomas and 11.8% for sessile serrated lesions (SSL). Predictors for identifying a precancerous polyp during colonoscopy included older age, history of prior colon adenomas, not having a previous colonoscopy at Mayo Clinic, and family history of CRC. A 6-tier LS adenoma/sessile serrated lesion (LASS) score was developed incorporating these factors. The median LASS score was 4 for lesion-positive colonoscopies and 3 for lesion-negative colonoscopies (P<.001). Adenoma and SSL detection rates increased with each additional LASS point. LASS points with corresponding adenoma and SSL detection rates were 0 (14.7%, 2.9%); 1 (17.8%, 8.9%); 2 (26.5%, 9.5%); 3 (35.0%, 12.5%); 4 (46.9%, 13.6%); 5 (57.8%, 15.5%).

The LASS score is a simple prediction tool for identifying patients with LS at higher risk of developing precancerous lesions. With no cases of PCRC, the precancerous polyp detection rates reported here could serve as quality benchmarks after validation.