Solitary fibrous tumor of the orbit with epithelioid features.

Extrapleural solitary fibrous tumors have often been confused with other mesenchymal tumors, such as hemangiopericytoma, fibrous histiocytoma, fibrous meningioma, and leiomyoma, because of morphologic similarity and underrecognition, especially if some unusual features are present. Recently, epithelioid solitary fibrous tumor has been reported in the mediastinum. We report a case of solitary fibrous tumor of the orbit with biphasic architecture, including spindle cell and epithelioid components. Both components demonstrated immunohistochemical features of a solitary fibrous tumor. A background of scattered vessels was present. No evidence of significant nuclear atypia or mitotic activity was noted. In this report, we discuss the differential diagnosis of solitary fibrous tumor with unusual epithelioid features. Extrapleural solitary fibrous tumor should be included in the differential diagnosis of tumors of the orbit with a spindle cell appearance even in the presence of some epithelioid morphology.