Colocutaneous fistula due to an infected sigmoid adenocarcinoma: A case report of an unusual revelation

Introduction and importance: As revealed as a colocutaneous fistula with an abscess in the abdominal wall, colon cancer is rare. It should be suspected in case of a painful abdominal wall mass in elderly patients. This case presentation of an infected sigmoid adenocarcinoma aims to highlight this uncommon presentation presenting some therapeutic issues. Case presentation: A 90-year-old woman with a past medical history of hypertension and major depressive disorder consulted the Emergency Department for lower left quadrant abdominal pain. The physical examination objectified a mild fever; lower left abdominal quadrant guarding, and abdominal mass of 10 cm with inflammatory signs. The abdominal CT scan showed a concentric thickness of the sigmoid colon with an abdominal wall abscess. She underwent an emergent laparotomy. Intraoperatively, we found an infected sigmoid tumour that invades the abdominal wall and is associated with a peritumoral abscess. This tumour was at the origin of the abdominal wall fistula. She underwent surgical drainage of the abscess, sigmoid colectomy, and colostomy. The postoperative follow-up was uneventful. The pathological examination of the operative specimen concluded with a colonic adenocarcinoma with lymph node invasion classified as pT4N2M0. Case discussion: Despite initial medical and radiological interventions, emergent surgery became necessary to address the infected sigmoid tumour invading the abdominal wall. Pathological examination revealed advanced cancer, but timely intervention and adjuvant therapy resulted in a positive outcome with no recurrence after two years. This case emphasizes the importance of recognizing unusual colon cancer presentations and the need for swift diagnosis and intervention. Conclusions: The diagnosis of colon cancer complicated with a colocutaneous fistula remains based on pathological examination after surgical management. These tumours presented an advanced stage and correlated to a poor prognosis. This highlights the interest in screening colonoscopy in front of any digestive symptoms in elderly patients.