S1655 Dealing With the Inevitable: A Case of Lynch Syndrome Not Meeting the Amsterdam Criteria

Abstract

INTRODUCTION: Lynch syndrome is one of the most common causes of hereditary colorectal cancer. The disease is mainly acquired by autosomal dominant inheritance and it has been found that 35% of patients diagnosed with colorectal cancer (CRC) have family history of neoplasia. The syndrome also places the patient at risk for extracolonic cancers including endometrial, brain, pancreas, stomach, among others. The most common cause of lynch syndrome is germline mutations of DNA mismatch repair genes. We present a case of Lynch syndrome in which the Amsterdam and Bethesda criteria were not met, however due to high suspicion, the disease was confirmed by genetic testing. CASE DESCRIPTION/METHODS: 33 years old Hispanic male that presented to our institution with 2 week history mild abdominal pain accompanied by weight loss. Computed tomography imaging was remarkable for concentric wall thickening of the transverse colon. Colonoscopy was performed and revealed a large mass in mid transverse colon occluding more than 90% of lumen which precluded further advance of scope. Pathology report of transverse colon biopsy revealed mucinous adenocarcinoma. Immunohistochemistry testing for mismatch repair proteins showed expression of MLH-1, MSH-2 and MSH6 and loss of nuclear expression of PMS2 which represented high probability of Lynch syndrome. The patient denied family history of colorectal cancer or any other Lynch syndrome related cancers. The patient underwent partial colectomy with resection of the adenocarcinoma. DISCUSSION: At the moment, there are no screening guidelines to detect Lynch-syndrome related cancers when Amsterdam criteria are not met. Once Lynch syndrome is diagnosed, screening is performed. It has been well documented in the literature that Lynch syndrome is frequently diagnosed when there is pertinent family history as established by Amsterdam and Bethesda criteria. Our case presents a patient with colorectal cancer with confirmed DNA mismatch repair genes consistent with Lynch syndrome, without family history Lynch syndrome related cancers. Mutations in PMS2 have a lower penetrance than other mutations, providing smaller increased risk of colorectal and endometrial cancer, but no increased risk of other Lynch syndrome related cancers. Mentioned findings can contribute to increase the awareness of this disease given the fact that 7% of individuals present with more than one related cancer at the time of diagnosis. By this means decreasing disease related complications and improving outcomes.