A rare case of perforated giant mesenteric fibromatosis causing acute peritonitis.

Desmoid tumors (DT) are rare benign tumors originating from myofibroblasts in the mesentery. Although benign, DTs exhibit local invasion and recurrence and may present sporadically or with familial adenomatous polyposis (FAP) and Gardner's syndrome. The clinical presentation ranges from asymptomatic abdominal masses to severe complications such as bowel obstruction and perforation. This case report highlights a 46-year-old male with acute diffuse peritonitis due to perforation of a mesenteric fibromatosis (MF). Imaging revealed a large mesenteric mass causing bowel perforation, necessitating an urgent exploratory laparotomy. Surgical intervention entailed resection of the affected small bowel and mesentery with temporary stoma formation. Histopathology confirmed MF with negative margins, and the patient was discharged in stable condition. This case highlights the importance of a multidisciplinary approach in managing such complex cases, the challenges in diagnosing and treating intra-abdominal DTs, and the role of surgical resection with careful postoperative monitoring despite recurrence concerns.