Intraorbital epidermoid

Findings

There is a well-circumscribed cystic lesion in an extraconal position within the left lateral orbit which traverses into the left temporal fossa. The lesion demonstrates fluid intensity with restricted diffusion and minimal capsular enhancement. There is mass effect on the lateral rectus and posterior left globe.

Differential diagnosis
- Intraorbital epidermoid
- Sebaceous cyst
- Venolymphatic lesion
- Lacrimal gland malignancy
- Rhabdomyosarcoma
- Dermoid


Diagnosis: Intraorbital epidermoid


Key points

Cyst-like mass lesion of the orbit resulting from congenital epithelial inclusion
Well demarcated, typically extraconal, mass with fluid-like or mixed contents
Most show thin, definable wall. Wall usually enhances post contrast
May demonstrate restricted diffusion
May demonstrate adjacent bony remodeling
65-75% occur in frontozygomatic suture in superolateral orbit
Clinical: usually painless mass; 10-15% present with rupture and secondary inflammation.
Acute inflammation mimics cellulitis or inflammatory rhabdomyosarcoma.
Mass effect may result in diplopia.
Surgical resection is curative.
Entire cyst must be removed to prevent recurrence.
Dermoids typically contain fat and appear heterogeneous, epidermoids have features similar to fluid and appear more homogeneous.