To report a case of a primary conjunctival epithelial cyst in the orbit.

A 60-year-old woman was referred for evaluation of proptosis of the left eye, which had developed about 2 years earlier. Upon initial examination, a movable mass was palpated in the medial aspect of the left orbit. Magnetic resonance imaging of the orbit showed a 2.5 cm-sized, ovoid, cystic mass located between the left eyeball and the medial wall of the orbit. Excisional biopsy of the orbital mass was performed. The orbital mass was a well-circumscribed cystic lesion, adherent to the medial rectus muscle. Histological examination revealed that the cyst was lined with multiple layers of cuboidal epithelium with goblet cells. A diagnosis of primary conjunctival cyst was made.

The possibility of primary conjunctival cyst should be considered in the differential diagnosis for an orbital cystic mass.