[Mesenchymal orbital tumors]

Mesenchymal tumors grow from pluripotent mesenchymal cells that form the soft orbital tissue. Primary tumors of the orbital walls are discussed in another section. Tumors from muscle and adipose tissue are rare or exceptional, except rhabdomyosarcoma, described in the section dedicated to pediatric tumors. Most frequent tumors are fibrous histiocytomas and solitary fibrous tumors, which often have a retrobulbar location. Fibrous histiocytoma is benign in only 65 % of cases. Fibrous solitary tumor is now better known (Ag CD34): this tumor is generally benign but frequently recurs.