Distal Duodenal Stricture Secondary to Mesenteric Fibromatosis (Intra-Abdominal Desmoid Tumor) of the Jejunum.

Introduction: Mesenteric fibromatosis (intra-abdominal desmoid tumor) is rare, with only a few cases reported in the literature. Clinical symptoms range from asymptomatic, nausea, early satiety, abdominal pain, and gastrointestinal bleeding. Although histologically benign, such a tumor may become locally invasive, and aggressive forms contribute to significant morbidity and mortality. Case Presentation: We report the case of a 52-year-old West African male with a 1-year history of intermittent hematochezia and intermittent bloating. Colonoscopy revealed a 4-mm rectal polyp and internal hemorrhoids. Esophagogastroduodenoscopy revealed a severe duodenal stricture 4-5 cm distal to the ampulla. Further work-up with contrast-enhanced computed tomography of the abdomen and pelvis revealed a 5.0 × 3.7 × 4.3-cm mass within the mesentery, encasing the distal portion of the duodenum. Exploratory laparotomy was performed, and the mass was excised from the jejunum. Histopathology findings and immunohistochemical analysis revealed the diagnosis to be mesenteric fibromatosis (desmoid tumor), positive for nuclear β-catenin and SMA, and negative expression of STAT6, desmin, caldesmon, pan-cytokeratin, or c-KIT. The Ki67 index is <1%. Conclusion: This case report highlights the diagnostic challenges of mesenteric fibromatosis due to its nonspecific clinical presentation. Recognizing uncommon presentations of mesenteric fibromatosis and risk factors aids in early diagnosis, management, and treatment. Importantly, this also aids in the prevention of complications such as intestinal obstruction, bowel ischemia, and fistula formation.