Atypical choristomatous cysts of the orbit

Background: The commonest choristomatous cysts of the orbit are dermoid and epidermoid cysts, which are lined by kerantinizing seuamous epithelium. They typically occur in the superior orbit, most commonly superotemporally. Other types, lined by different epithelia, and other orbital sites are much less common. Methods: Five cases of atypical orbital cystic choristomas that presented over the past 6 years are reported. The clinical and radiological features, surgical approach and findings, and histology are described. Similar cases from the literature are reviewed, and possible aetiology discussed. Results: Four of the cysts were lined by a non-keratinizing epithelium resembling conjunctiva; two had adnexal structures in their walls. Compared with typical dermoid and epidermoid cysts, these ‘conjunctival dermoids’ and ‘conjunctival cysts’ of the orbit tended to present later in life, none were associated with bony defects, and three of the four occurred in the superomedial quadrant. One case occurred inferiorly, a rare site for orbital conjunctival dermoids and cysts, or typical dermoids and epidermoids. The fifth case, also inferior; is an example of a cyst within choristomatous lacrimal tissue. Conclusion: Choristomatous cysts of the orbit may occur with non-keratinizing epithelial linings, and such cysts tend to differ clinically from the commoner dermoids and epidermoids. They may also occur in atypical sites such as the inferior orbit.