Background: Patients with 10 or more lifetime adenomas are candidates for genetic counseling and testing for polyposis syndromes. Lynch syndrome falls under the umbrella of hereditary nonpolyposis colorectal cancer, and it is assumed that patients with Lynch syndrome do not develop multiple adenomas.
Objective: The objective of this study was to document the number of adenomas in patients with Lynch syndrome.
Design: This was a retrospective review of clinical, colonoscopy, and pathology records of patients with Lynch syndrome in a prospectively maintained hereditary colorectal cancer database.
Settings: The study was conducted at a single-institution tertiary care center with specialized practice in hereditary colorectal cancer syndromes.
Patients: We included 263 patients with a germline mutation in 1 of the 4 DNA mismatch repair genes.
Interventions: Colonoscopy and polypectomy were the study interventions.
Main outcome measures: The lifetime cumulative number of colorectal adenomas and their characteristics were measured.
Results: A total of 107 of the 263 patients had 1 or more adenomas. Sixty-one patients had 1 adenoma, 29 (11%) had 2 to 5 adenomas, 6 (2%) had 6 to 9 adenomas, and 11 patients (4%) had 10 or more cumulative adenomas. The maximum number of synchronous adenomas in any individual was 22, and the maximum number of cumulative adenomas in any individual was 24. Twenty-four of the 107 patients with adenomas underwent a total colectomy or proctocolectomy and were excluded from long-term follow-up. In the remaining 83 patients with adenomas, 426 colonoscopies were performed. A total of 220 (54%) were normal or had hyperplastic polyps; 313 adenomas were found in 206 examinations (46%), and 123 (39%) of the adenomas were advanced.
Limitations: There was variability in the interval of colonoscopy surveillance. Some patients had a variant of unknown significance and were separated from those with a deleterious mutation.
Conclusions: Although 10 or more adenomas prompt testing for polyposis syndromes, Lynch syndrome should also be considered in the differential diagnosis.