Leiomyoma of the orbit.

A 5-year-old boy had a one-year history of inability to adduct the left eye and redness. Examination showed a medial orbital mass indenting the globe without proptosis. A well-encapsulated mass was removed surgically. On light microscopy it seemed to be a neurofibroma. Transmission electron microscopy showed that the tumor was composed of cells with cigar-shaped nuclei, cytoplasmic and plasmalemmal densities, fine filaments, surface-connected vesicles, and basement membrane. These features were characteristic of leiomyoma.