When should bladder cancer prompt evaluation for Lynch syndrome? An evidence-informed clinical framework

Lynch syndrome (LS) is an established cause of urothelial cancer, yet hereditary evaluation remains far better defined for upper tract urothelial carcinoma than for bladder cancer. The clinically relevant question is not whether bladder cancer belongs to the LS spectrum, but when a bladder cancer diagnosis should prompt evaluation for previously unrecognized LS. This mini-review examines the clinical and molecular findings that may justify hereditary assessment in patients presenting with bladder cancer and proposes an evidence-informed framework for their interpretation. The strongest signals include a known familial LS variant, a personal or family history of LS-associated malignancy, and tumor evidence of mismatch repair deficiency, microsatellite instability, or a pathogenic MMR alteration. Previous or synchronous upper tract disease and younger age may increase suspicion, whereas tumor grade alone is insufficiently specific. Tumor testing should guide, but not replace, germline evaluation, and negative tumor findings do not fully exclude hereditary disease when clinical suspicion remains high. Confirmation of LS has clear implications for lifelong cancer prevention and cascade testing, while its effect on bladder cancer treatment and urologic surveillance remains uncertain. Prospective bladder-specific studies are needed to validate testing strategies and define clinical actionability.