Background: Two patients, a 13-year-old girl and a 31-year-old man, had an orbital dermoid tumor located in the lateral rectus muscle. This unusual location of dermoid tumors has not been reported previously.
Methods: Computed tomography and magnetic resonance imaging showed a cystic mass within the belly of the lateral rectus in each patient. Surgical excision through a lateral orbitotomy showed a well-circumscribed mass surrounded by lateral rectus fibers. No periorbital attachment was noted.
Results: Results of histopathologic evaluations showed a dermoid cyst. Postoperatively, the diplopia and proptosis resolved. In one patient, an unusual subconjunctival deposition of fat droplets was seen.
Conclusion: The findings in patients demonstrate an unusual presentation of dermoid cysts and make an addition to the differential diagnosis of enlarged extraocular muscles.