Benign fibrous histiocytoma of the medial rectus muscle.

We report the case of a healthy 17-year-old girl who underwent surgery for excision of a painless, rapidly enlarging subconjunctival mass. The mass was found to be tightly adherent to the medial rectus muscle of the left eye, requiring extensive dissection. Histopathology revealed a mass of bland and foamy spindle cells in a storiform pattern that was positive for CD68, PGM1, and factor XIIIA and negative for S-100. The clinical and histopathologic findings are consistent with benign fibrous histiocytoma.