Orbital cysts may arise from a variety of ocular surface or orbital tissues and include cysts derived from the conjunctival or eyelid epithelium, teratomatous cysts, neural cysts, secondary cysts (mucoceles), inflammatory cysts (parasitic), and noncystic lesions with a cystic component. Orbital cysts can be developmental or acquired in origin. Dermoid cyst is a developmental lesion and the most common type of orbital cyst.
Dermoid cysts are believed to occur when surface ectodermal nests become entrapped in the bony sutures during embryogenesis. Most of these cysts manifest in childhood as a unilateral mass in the lateral brow. Histologically, a dermoid cyst is lined by keratinized stratified squamous epithelium and contains keratin, sebum, and hair. By definition, its walls contain dermal appendages, including sebaceous glands, hair follicles, and sweat glands (Fig 14-1). If the cyst wall does not have adnexal structures, the term simple epithelial (epidermoid) cyst is applied. Simple epithelial cysts may also be lined by respiratory, conjunctival, or apocrine epithelium.
Rupture of a dermoid cyst may cause a marked granulomatous reaction, largely due to the presence of sebum in the cyst lumen.
Figure 14-1 Orbital dermoid cyst. A, Clinical photograph of dermoid cyst of the right orbit. Note the typical superotemporal location. B, Low-magnification photomicrograph reveals a cyst lined by keratinized stratified squamous epithelium and containing keratin. The sebum dissolves out of the lumen during histologic processing. C, The cyst wall contains sebaceous glands (arrows) and adnexal structures.
(Part A courtesy of Sander Dubovy, MD; part B courtesy of Nasreen A. Syed, MD; part C courtesy of Hans E. Grossniklaus, MD.)
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.