This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Radiology
[{'content': 'Fat ring sign is positive in? \nSelect and explain. \nA. Mesenteric panniculitis, B. Lymphoma, C. Carcinoid, D. Desmoid tumor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans AFat ring signQ is preservation of fat around the mesenteric vessels and around soft tissue nodules on a background of fat stranding in mesenteric panniculitis or mesenteric lipomas. Also known as a fat halo sign', 'role': 'assistant'}]