Orbital granular cell tumor developing in the inferior oblique muscle.

Abstract

To describe the magnetic resonance imaging and histopathologic features of an orbital granular cell tumor. A 43-year-old man was initially examined with slowly progressive vertical diplopia. A firm mass was palpable through the left lower eyelid. Magnetic resonance imaging and histopathologic examinations were performed. Magnetic resonance imaging disclosed a spindle-shaped mass involving the inferior oblique muscle. Histopathologic examination disclosed that the tumor cells, diagnosed as a granular cell tumor, had infiltrated the muscle fibers. In the present case, these findings indicate that the granular cell tumor may develop in the inferior oblique muscle.