S3539 The Importance of Taking a Family History: Diagnosis of Lynch Syndrome After Direct Access Colonoscopy

Abstract

Introduction: Lynch Syndrome (LS) is a familial cancer-predisposition syndrome caused by mutations in DNA mismatch repair genes. LS accounts for 3-8% of all new cases of colorectal cancer (CRC), and it increases the lifetime risk of multiple associated cancers. LS is common, occurring in approximately 1 in 200-300 individuals, but remains underdiagnosed. Estimates indicate that less than 1% of individuals with LS are aware of their diagnosis. This represents a missed opportunity for cancer screening and prevention. Case Description/Methods: A 50-year-old healthy woman presented to endoscopy for direct access screening colonoscopy. Family history included in her electronic medical record noted two malignancies in first degree relatives (thyroid and uterine). Colonoscopy revealed 13 tubular adenomas (3- 12mm). Office follow up to discuss genetic testing was delayed due to COVID-19. 10 months later the patient presented for follow up, and family history revealed ureteral and CRC in her father, CRC in her paternal uncle, and uterine cancer in her paternal aunt and paternal grandmother. Germline genetic testing was discussed and sent. While awaiting results, she was found to have atypical endometrial cells on routine pap smear. Colposcopy revealed complex endometrial hyperplasia (CAH) with atypia, bordering on grade 1 endometrioid carcinoma. The following week, genetic results showed a mutation in MSH6. One week later, surveillance colonoscopy revealed 4 sub-cm tubular adenomas. She then underwent total hysterectomy, bilateral salpingo-oophorectomy, and sentinel lymph node biopsy. Pathology showed CAH but no definitive features of endometrioid carcinoma. The patient recovered from her surgery uneventfully, is now in a screening/surveillance program, and cascade testing has begun for her first-degree relatives, including her two adult children. Discussion: This case highlights the importance of obtaining cancer family history during patient contact, so that this underdiagnosed condition can be identified and patients can benefit from appropriate cancer screening..