The nomenclature and etiology of "dermoid" tumors and fatty lesions of the orbit and ocular adnexa have created longstanding confusion.

Most of these tumors present in the temporal orbit as smooth growths, but their histologic and anatomic distinctions dictate different management approaches. Therefore, it is important to differentiate these lesions clearly. We classify these lesions into epidermoid and dermoid cysts, dermolipomas (limbal dermoids), lipodermoids, lipomas, and herniated orbital fat.

Figure 1: Axial CT of the head demonstrating epidermoid cyst extending through frontozygomatic suture of right lateral orbital wall.

Dermoid and epidermoid cysts Dermoid and epidermoid cysts arise from sequestration of epithelial tissue (ectoderm) at bony junctions, most commonly the frontozygomatic suture (Figure 1).¹ These choristomas are the most common orbital lesions of childhood.^2-4 Although clinically indistinguishable, epidermoid cysts lack dermal tissue while dermoid cysts contain both dermis and epidermis.

Figure 2: External photograph of right epidermoid cyst at frontozygomatic suture.

While these lesions can be differentiated histologically, presentation and management are identical. Epidermoid and dermoid cysts are typically temporal lesions located adjacent to or extending through the frontozygomatic suture in children (Figure 2). These lesions are typically smooth and noninflammatory. Complete excision of the cyst with its capsule is recommended, because residual tissue may cause significant inflammation or recurrence. A similar clinical picture occurs after traumatic rupture of the cyst.

Axial displacement of the globe is a more common presentation in adults when the undetected cyst has slowly enlarged in the deep orbit. Another unusual presentation is that of a nasal orbital cyst originating from the conjunctival epithelium of the caruncle instead of the skin.

Figure 3: External photograph of left dermolipoma (limbal dermoid) demonstrating hair on its surface.

Dermolipomas and lipodermoids Dermolipomas and lipodermoids are choristomas composed of both ectodermal and mesodermal elements.^5,6 They are the most common peribulbar tumors of childhood.^2,7,8 The dermolipoma is the classic "limbal dermoid" (Figure 3) composed primarily of fibrous tissue while the lipodermoid has a predominantly fatty component. Histologically, dermolipomas may demonstrate pilosebaceous units, fat, teeth, and bone.

Figure 4 External photograph of lipodermoid adjacent to the globe in the left temporal orbit.

On the other hand, lipodermoids are predominantly fatty tissue. Lipodermoids are usually located in the temporal orbit adjacent to the globe (Figure 4). Both of these solid choristomas should be differentiated from their cystic counterparts described above.

Although lipodermoids and dermolipomas usually can be distinguished clinically, they are managed quite differently. Lipodermoids are usually only cosmetic deformities. However, overaggressive removal can very easily lead to functional problems such as restrictive conjunctival scarring and strabismus. These lesions very often adhere to the overlying conjunctiva and adjacent extraocular muscles. The keys to undertaking their removal are to preserve conjunctiva and to remember that complete removal is not necessary. Excision should only be attempted after an extensive discussion of the risks and benefits with the patient and/or parents.

Dermolipomas, on the other hand, often cause functional problems such as astigmatism, foreign-body sensation, and dellen.⁹ Amblyopia evaluation should be part of the treatment plan in children. Dermolipoma excision can be complicated by thin or absent underlying sclera and an increased risk of ocular perforation.¹⁰ Also, removing lesions extending into the cornea can leave significant stromal scarring. Some authors advocate lamellar keratoplasty or patch grafts in these situations.^11,12 The clinical association of dermolipomas with Goldenhar's syndrome may also have diagnostic and management ramifications for these patients.