To report a case of orbital invasion of ameloblastoma.

A 69-year-old male patient was referred to the ophthalmologist from an otorhinolaryngology clinic due to mass invasion of the orbit on computed tomography. The patient had a history of ameloblastoma of the left maxilla, which had been diagnosed in 1988, and for which he had undergone left maxillectomy. He was transferred from a private hospital because of suspected tumor after frequent epistaxis at the left nasal cavity of about 1 year. The biopsy report confirmed that the mass was a recurrence of the ameloblastoma, and a 17.4 × 22.7 × 23.5-mm-sized mass that filled the left ethmoid sinus and invaded the nasal side of the orbit was found on paranasal sinus magnetic resonance imaging. There was no limitation of eye movement in any field of gaze in the left eye even though the patient reported diplopia. After maximum resection of the tumor using a debrider with endoscope, the size of the tumor was reduced and the symptom of diplopia was resolved. The patient will undergo continuous follow-up.

Ameloblastoma is rare among orbital tumors originating from the paranasal sinus. We experienced a case of maxillary ameloblastoma involving the orbit. However, close monitoring should be administered to patients with such a tumor.