This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Fibrous histiocytoma involves most commonly: 
Select and explain. 
A. Eyelid, B. Epibular, C. Intraocular, D. Orbit
D: Orbit
Answer: D: Orbit 
Explanation: Fibrous histiocytoma is the most common primary mesenchymal orbital tumor in adults. 
It may involve ocular structures such as the orbit, lids, conjunctiva, and ocular limbus. 
Most fibrous histiocytomas are benign, but some are locally aggressive and malignant.