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Editor,

Dermoid cysts are the most common cystic lesions to be found in the orbit (Sathananthan et al. 1993). The cyst is a congenital lesion that forms from epithelial cells that are trapped during embryogenesis beneath the surface epithelium, often near bony structures. Superficial dermoids are noticed during the first years of life, but those that are located more deeply do not become clinically evident until the subject is 15–40 years of age. They frequently occur near the orbital rim superotemporally at the frontal zygomatic structure, but can occur at other bony structures and in deeper intraorbital components where they are connected through a defect in the bone (dumbbell-shaped dermoid) and may even involve several bones and grow intracranially (Rumelt et al. 1997; Blanco et al. 2001). Although dermoid cysts are benign, carcinoma can arise from the epithelium (Holds et al. 1993).

A 40-year-old man was referred with a growing mass situated at the lacrimal gland of the left eye. It had not caused any visual problems. Exophthalmometry showed a 3-mm exophthalmos of the left eye (17-20/106 mm). Clinical examination showed a second, soft mass adjacent to the zygomatic process. Computed tomography (CT) showed a dumbbell-shaped dermoid cyst, perforating the frontal zygomatic structure (Fig. 1).

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Figure 1.  Computed tomography scan of patient 1. The arrowhead shows the cyst penetrating the bone at the frontal zygomatic structure.

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To enable an en-bloc excision, a Krönlein incision was performed. The periosteum was incised and the dermoid cyst was exposed in the lateral fossa. The cyst was filled with translucent fluid. The zygoma was sawn through beneath and above the bony defect to facilitate the removal of the dermoid cyst through the canal (Fig. 2). Following careful dissection, the multi-lobular yellowish cyst was removed in one piece. The bony canal was then burred and cleaned with alcohol to remove any dermoid fragments, after which the bone fragment was replaced. Histopathologically, the cyst (measuring 2 × 2 × 2.6 cm) was lined with mostly keratinizing squamous epithelium and contained sebaceous material. The cyst wall contained hair follicles and sebaceous glands (Fig. 3).

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Figure 2.  Patient 1: intraoperative view showing the bi-lobed cyst (arrow) through the sawn bone defect.

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Figure 3.  Patient 1: histopathology of the cyst showing many goblet cells and one hair follicle.

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A second patient, a 21-year-old White man, presented with a mass behind the right eyelid that had become evident to him when he examined a recent photograph. Retrospectively, this patient was able to identify a slight protrusion in photographs taken from his ninth year onwards. Computed tomography and magnetic resonance imaging (MRI) (Fig. 4) showed a dumbbell-shaped mass penetrating the zygomatic bone. This was excised using a lateral orbital approach with extraction of both parts of the dermoid and zygoma bone segments. Extensive bone enlargement and the very oblique course of the cyst within the zygoma made it impossible to remove the cyst intact, and therefore each part was bound with vicryl and removed separately. The cyst was filled with a yellow–white thick fluid. The clinical diagnosis was confirmed histopathologically.

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Figure 4.  MRI scan of patient 2, showing the defect in the zygomatic structure (arrow).

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Although dermoid cysts are benign, management ranges from observation to surgical excision. Most of them are removed surgically because the patient presents with a cosmetically visible lesion or ocular symptoms caused by the rupture of the cyst and orbital inflammation (caused by the constant leaking of the cyst contents, which can include fat, mucous or granulomatous fluids). An anteriorly located orbital dermoid cyst can be excised via a cutaneous or conjunctival approach (Rootman 2003). A deeper cyst may require a lateral orbitotomy. Care should be taken to avoid surgical rupture of the cyst. If rupture occurs, vigorous irrigation and instillation of antibiotics or corticosteroids are advisable to prevent postoperative inflammation. Additional precautions against recurrence require the bony canal to be burred through to remove any small remnants.

In summary, dumbbell-shaped dermoid cysts should be excluded with palpation of the periorbital region. Special attention should be given to CT and MRI scans when the dermoid is fixed to the underlying bones, particularly in the region of the frontal zygomatic structure. Very careful extirpation of the orbital wall is required during surgical procedures involving dumbbell-shaped dermoid cysts.

References

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  2. References
  • Blanco G, Esteban R, Galaretta D & Saornil A (2001): Orbital intradiploic giant epidermoid cyst. Arch Ophthalmol 119: 771773.
  • Holds JB, Anderson RL, Mamalis N, Kincaid MC & Font RL (1993): Invasive squamous cell carcinoma arising from asymptomatic choristomatous cysts of the orbit. Two cases and a review of the literature. Ophthalmology 100: 12441252.
  • Rootman J (2003): Diseases of the Orbit. A Multidisciplinary Approach. Lippincott, Williams & Wilkins, Philadelphia, PA, USA 418420
  • Rumelt S, Harsh GR IV & Rubin PA (1997): Giant epidermoid involving three cranial bones. Arch Ophthalmol 115: 922924.
  • Sathananthan N, Moseley IF, Rose GE & Wright JE (1993): The frequency and clinical significance of bone involvement in outer canthus dermoid cysts. Br J Ophthalmol 77: 789794.