Laboratory Studies
The diagnosis of a limbal dermoid requires a directed clinical examination. Specific laboratory studies are generally not necessary.
Imaging Studies
MRI
Some dermoids may appear to extend into the conjunctival fornix or lateral canthus. These lesions may contain connective tissue that entangles with the orbital fat and muscle tissue belonging to the extraocular muscles.
Radiologic imaging with an MRI can be useful in identifying such lesions, especially if surgical management is being considered.
Procedures
Biopsy is not necessary, except in rare instances when the diagnosis is doubtful.
Histologic Findings
Limbal dermoids contain choristomatous tissue, including epidermal appendages, adipose and lachrymal gland tissue, smooth and striated muscle, cartilage, brain, teeth, and bone. Lymphoid nodules and vascular elements also have been reported. Immunohistochemical studies have demonstrated that limbal dermoids share antigenic expression with the basal limbal epithelium and the stem cell niche of normal human hair follicles. [9] The surface of the dermoids consists of corneal or conjunctival epithelium. The lesion may be cystic or solid. Note the histological image below.
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Limbal dermoid in the left eye of a 13-year-old male patient.
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Histopathological section demonstrating a pilosebaceous unit.
