Conjunctival Implantation Cyst in the Orbicularis Oculi Muscle: Review of a Possible Origin From Displaced Stem Cells With a Differential Diagnosis

PURPOSE

To document a unique case of a corneal/conjunctival epithelial inclusion cyst located in the orbicularis oculi muscle with a comprehensive review of variant conjunctival cysts and simulating conditions.

METHODS

Clinicopathologic case report with detailed histopathologic and immunohistochemical evaluation for cytokeratins combined with a tabulation of mimicking lesions and relevant literature citations.

RESULTS

A 59-year-old man experienced severe blunt left periorbital trauma that resulted in a limbal partial-thickness corneal wound with an associated epithelial abrasion and a full-thickness eyelid laceration extending from the superior fornix to the margin. Several months after surgical repair of the eyelid a cyst appeared in the superior pretarsal skin. Histopathologic and immunohistochemical investigations supplied data suggesting that the cyst had a high probability of a corneoscleral limbal stem cell origin. Distinctive features of the lesion are contrasted with those of allied or simulating cysts.

CONCLUSIONS

Stem cells are now believed to be located at the corneoscleral limbus, in the inferior fornix, in the medial canthal region, and at the eyelid margin where transitions from conjunctival epithelium to epidermal epithelium occur. Due to their replicative, hardy and robust nature, stem cells displaced to alien environments are most likely to survive and produce cysts. The cyst's corneal-type cytologic characteristics, the absence of goblet cells, and the expression of a broad spectrum of cytokeratin biomarkers in the current case give support to the proposal that limbal stem cells in the region of the corneal laceration were displaced to the eyelid orbicularis muscle and were responsible for this most extraordinary cyst. Comparison with other epithelial cystic linings lends further evidence for this conclusion.

Characterization of the parasite-induced lesions in the posterior segment of the eye

Ocular lesions are frequently associated with different parasitic infections. The classes of infection include protozoa, nematodes, cestodes, and ectoparasites. Ocular parasitic infections can manifest in any part of the eye; the disease manifestations are frequently characterized as either posterior or anterior eye disease. Parasite-induced lesions may be due to damage directly caused by the parasite, indirect pathology caused by toxic products or the immune response initiated by infectious parasitism. This review characterized the parasite-induced lesions in the posterior segment of the eye. Prompt diagnosis and early treatment of these lesions can reduce ocular morbidity. The method of the literature search was conducted on PubMed, Elsevier Scopus database, and Google Scholar with no limitation on the year of publication databases. It was limited to English articles published for ocular lesions in clinical studies and was focused on parasitic infections of the eye.

A primary orbital hydatid cyst

Echinococcosis, caused by the tapeworm Echinococcus granulosus, is an endemic zoonosis in which humans act as accidental intermediate hosts. Orbital hydatid cysts comprise 1% to 2% of all hydatid lesions. We describe a 10-year-old boy with an orbital hydatid cyst. The orbital cyst was removed totally by frontal craniotomy and orbitotomy. It should be noted that unilateral painless proptosis in patients from countries endemic for echinococcosis could be caused by an orbital hydatid cyst.