Dermoid cyst

Diagnosis Definition

• Dermoids are benign, ectoderm-lined inclusion cysts that can contain hair, sebaceous and sweat glands, and squamous epithelium
• Most are congenital but they can also be iatrogenic or traumatic from puncture wounds
• They are typically slowly expanding, unilocular, cystic masses with mild symptoms
• Only 7% of dermoid cysts occur in the head and neck, with the most reported common locations being the lateral eyebrow region and the floor of the mouth; in addition, many are small but palpable superficial lesions embedded in the skin and subcutaneous tissue

Imaging Findings

• Although unilocular, dermoid cysts may have internal septations and/or lipid material floating like supernatant “oil on water” over heavier proteinaceous debris
• The imaging appearance on CT and MRI is variable, ranging from homogeneous fluid to heterogeneous attenuation/signal intensity due to keratinaceous and sebaceous content
• The cyst wall is typically thin or non-perceptible but can become thick and radiologically visible; this thick lining can calcify and enhance
• The sebaceous, lipid material in a dermoid has the attenuation and signal intensity of fat on both CT and MR images; a fat/fluid level is very suggestive of a dermoid cyst

KEY IMAGES

Pearls

• An inflammatory reaction can occur if a dermoid cyst is disrupted, and the cyst can recur if not completely excised
• When the fat content coalesces into small globules within the fluid matrix, dermoid cysts have a so-called “sac of marbles” appearance

References

1. Koeller KK, Alamo L, Adair CF, et al.  Congenital cystic masses of the neck: radiologic-pathologic correlation. RadioGraphics 1999; 19:121-146
2. Smirniotopoulos JG, Chiechi MV.  Teratomas, dermoids, and epidermoids of the head and neck. RadioGraphics 1995; 15:1437-1455