Dermoid Cyst

This asymptomatic swelling above a 3-month-old boy's left eyebrow had not changed since birth. The 15 × 13-mm, soft, nontender, freely mobile nodule had no punctum, hair tuft, or other skin anomaly (A). The infant was born at term and was otherwise healthy. At the parents' request, the nodule was excised without complications by a pediatric surgeon. Pathological findings showed lamellated keratin within the mass and surrounding pilosebaceous units opening into the mass, consistent with a dermoid cyst (B).

Courtesy of Lisa Edsall, MD.

Dermoid cysts are so named because they reproduce the components of normal dermis histologically.¹ These epithelial-lined cysts result from retained epithelium along embryonic fusion planes. They contain adnexal structures, such as sebaceous, apocrine, or eccrine glands and hair follicles. The cysts can be found subcutaneously—as in this patient—or in the abdominal, cranial, and spinal cavities. Cutaneous dermoid cysts often present at or shortly after birth as small (1- to 4-cm) rubbery nodules.² They tend to occur along embryonic fusion lines, most commonly along the lateral third of the eyebrow, scalp, and nose.³ The cysts are nontender, unless ruptured, and may slowly enlarge. The overlying skin appears normal and is freely mobile.

Potential complications include infection, rupture, and abscess formation. Midline or nasal dermoid cysts may connect with the CNS through sinus tracts; bacterial entry can result in meningitis.⁴ Cysts overlying the spine may connect directly with the spinal cord and can be a sign of incomplete fusion of the posterior midline embryonic structures. Cysts may also adhere to the periosteum or cause pressure erosions of underlying bone.⁵ Rarely, osteomyelitis may develop.

The treatment of dermoid cysts is surgical excision. Incomplete removal can result in recurrence. For cysts in the midline of the face and scalp, a preoperative CT or MRI scan is essential because of possible intracranial extension. Consultation with a neurosurgeon, otolaryngologist, or plastic surgeon may be indicated.