Metachronous Mesorectal Recurrence after Colectomy for Ascending Colon Cancer

Background: An isolated metachronous recurrence in the mesorectum from a primary ascending colon cancer is a rare finding that has not been previously reported. This may represent a form of retroperitoneal spread, sometimes referred to as “drop metastasis,” which is an uncommon mechanism for metachronous recurrence. Case Presentation: A 38-year-old male presented to the Emergency Department in January of 2018 with profound anemia. A colonoscopy revealed innumerable colonic polyps. He reported having multiple family members diagnosed with colon cancer and was subsequently diagnosed with familial adenomatous polyposis with rectal sparing. Total abdominal colectomy with ileorectal anastomosis was performed, revealing a T3N1a adenocarcinoma of the ascending colon. The patient subsequently underwent 12 cycles of adjuvant FOLFOX. Surveillance imaging in late 2019 revealed a suspicious mass in the superior perirectal soft tissue without any other sites of potential disease. Completion proctectomy was performed in January 2020, 2 years after the initial resection. Pathology revealed a mesorectal tumor deposit located 1.5 cm distal to the ileorectal anastomosis. No evidence of mucosal involvement or nodal metastasis was identified. Conclusion: Isolated mesorectal recurrence is a rare and previously unreported clinical finding following resection of an ascending colon cancer with an ileorectal anastomosis. This likely represents a form of retroperitoneal spread.