Solitary fibrous tumor of the tongue: report of a case with immunohistochemical and ultrastructural studies.

Solitary fibrous tumors are rare in extrapleural sites and extremely rare in the oral cavity. We report a case of a solitary fibrous tumor arising from the tongue of a 70-year-old woman. The tumor measured 1.6 cm in maximum diameter and consists of spindle-shaped cells distributed in a haphazard pattern. Immunohistochemical studies show strong positivity for CD34 and bcl-2, and weak positivity for desmin. Smooth muscle actin and S-100 protein are negative. Electron microscopy shows uniform neoplastic spindle cells with mesenchymal features. The differential diagnosis for spindle cell neoplasms in the tongue is discussed.