Twists of the Gut and Genome: A Case of Intestinal Intussusception Revealing Lynch Syndrome in a Young Adult and Literature Review.

Adult intussusception is a rare clinical entity and often indicates an underlying organic pathology, particularly malignancy. Unlike pediatric cases, adult intussusception necessitates oncologic evaluation and surgical management. We present a case of a 32-year-old woman with no family history of colorectal cancer who presented with a three-month history of intermittent abdominal pain, which had worsened recently. Computed tomography imaging revealed a target-like lesion in the cecum and ascending colon, consistent with ileocolic intussusception. Exploratory laparotomy identified a 10 cm intussuscepted segment with a thickened bowel wall and regional lymphadenopathy. A right hemicolectomy with en-bloc resection and lymphadenectomy was performed. Histopathology confirmed a poorly differentiated tubular adenocarcinoma invading the muscularis propria (T2N0M0) without lymph node involvement. Immunohistochemistry demonstrated loss of MLH1, MSH2, and MSH6, consistent with microsatellite instability-high (MSI-H) phenotype. Genetic testing confirmed Lynch syndrome. The postoperative course was uneventful, and the patient was discharged on postoperative day five without the need for adjuvant chemotherapy. Ileocolic intussusception in young adults may be the initial presentation of colorectal malignancy, including hereditary cancer syndromes. Timely surgical resection and genetic evaluation are crucial for diagnosis, staging, and long-term management.