A Rare Case Report of Small Bowel Mesenteric Desmoid Tumor with Perforation and Abscess

Desmoid tumors (DTs) are slow-growing tumors with no malignant or metastatic features but are locally invasive. These tumors have an unpredictable but varied clinical course. Intra-abdominal sporadic DTs are very rare and have a worse prognosis due to the mass effect on abdominal organs. This paper reports the diagnostic and surgical treatment of a 34-year-old man with DT of the small intestine without any genetic predisposing factor or history of trauma and abdominal surgery. The patient initially had mild pain in the periumbilical area and then presented with exacerbation of abdominal pain, acute abdominal symptoms, and peritonitis during elective diagnostic procedures. Abdominal CT scan with contrast injection showed a hypodense area with irregular borders and open-air foci of 171*160*85 mm in the middle of the abdomen and displacement of intestinal loops. Diagnostic and therapeutic laparotomy revealed a very large mass (18 cm in diameter) in the mesentery of a large part of the small intestine, a purulent abscess adjacent to the mass, and perforation of the D4 part of the duodenum. Debulking resection of the tumor was performed due to the involvement of the upper mesenteric artery. Preoperative elective core needle biopsy, surgical biopsy, and immunohistochemistry reports revealed desmoid tumor. Desmoid tumor as a benign tumor can have aggressive manifestations similar to intra-abdominal malignancies.