Where is the mass located?
It's located within the left side of the small bowel mesentry
What is the differential diagnosis for a mesenteric mass?
Benign mesenteric masses include lymphangiomas and mesentric cysts, but neither fits the imaging characteristics. Lipoblastoma is a benign fatty mass that occurs in children and clearly isn't the cause here. Primary mesenchymal or stromal tumours of the mesentry resemble either retroperitoneal sarcomas (most commonly leiomyosarcoma) or GIST. Other masses include mesenteric desmoid, lipodystrophy (retractile mesenterisitis and mesenteric paniculitis), and lymphadenopathy.
Of the differential offered, what is the most likely diagnosis?
Mesenteric desmoid, also called mesenteric fibromatosis, is most likely.
Large left-sided abdominal mass with soft-tissue attenuation.