The correct answer is:
B) Colonoscopy every 1–2 years
This patient has Lynch syndrome (hereditary nonpolyposis colorectal cancer), an autosomal dominant disorder caused by mutations in DNA mismatch repair genes such as MLH1, MSH2, MSH6, and PMS2. The strong family history of early-onset colorectal and endometrial cancers is highly characteristic. Unlike familial adenomatous polyposis (FAP), Lynch syndrome does not produce hundreds of polyps. Instead, affected individuals develop relatively few adenomas that progress rapidly to carcinoma because DNA replication errors accumulate unchecked.
The mismatch repair system normally corrects errors that occur during DNA replication. Defects in this pathway produce microsatellite instability and dramatically increase the risk of colorectal cancer as well as several extracolonic malignancies, particularly endometrial cancer. Other associated cancers include ovarian, gastric, pancreatic, urinary tract, and small bowel malignancies.
Because the adenoma-carcinoma sequence is accelerated in Lynch syndrome, surveillance must be far more frequent than in average-risk individuals. Colonoscopy every 1–2 years beginning in early adulthood significantly reduces cancer-related mortality and is a cornerstone of management.
A common board question asks learners to distinguish Lynch syndrome from FAP. FAP produces massive numbers of adenomas and requires prophylactic colectomy, whereas Lynch syndrome produces relatively few polyps but requires intensive surveillance because cancer develops rapidly.
Answer choice A: Annual fecal immunochemical testing only, is incorrect.
Fecal immunochemical testing (FIT) is not sufficient for patients with Lynch syndrome. Direct visualization with colonoscopy is necessary because of the markedly increased cancer risk.
Answer choice C: Colonoscopy every 10 years, is incorrect.
Ten-year intervals are appropriate for average-risk patients with a normal colonoscopy. Lynch syndrome requires substantially more frequent surveillance.
Answer choice D: Repeat colonoscopy at age 50, is incorrect.
This recommendation would be appropriate for some average-risk screening strategies but would dangerously delay surveillance in a patient with a hereditary cancer syndrome.
Answer choice E: Surveillance is unnecessary after adenoma removal, is incorrect.
Removal of a single adenoma does not eliminate the underlying genetic predisposition. Lifelong surveillance remains essential.
Key Learning Point
Lynch syndrome is caused by DNA mismatch repair defects and is associated with early-onset colorectal and endometrial cancers. Colonoscopy every 1–2 years is recommended because of accelerated progression from adenoma to carcinoma.
