Teratomas, dermoids, and epidermoids of the head and neck.

Dermoids and epidermoids are ectoderm-lined inclusion cysts that differ in complexity: Epidermoids have only squamous epithelium; dermoids contain hair, sebaceous and sweat glands, and squamous epithelium. Both arise from trapped pouches of ectoderm, near normal folds, or from failure of surface ectoderm to separate from the neural tube. These slowly expanding, unilocular, cystic masses may produce only mild symptoms. They commonly occur in the orbit, calvarial diploic space, and intracranially (the posterior and middle fossae). They may be complicated by rupture leading to chemical meningitis, and dermoids with a fistulous tract can become infected. Craniofacial teratomas are true neoplasms arising from misplaced embryologic germ cells. They contain a medley of heterogeneous tissues, typically reflecting more than one of the three embryonic germ layers. They are usually multiloculated masses, often large, with complex radiologic characteristics. Craniofacial teratomas may manifest prenatally with macrocrania or polyhydramnios, during a difficult delivery, or postnatally as a life-threatening mass causing brain herniation, hydrocephalus, respiratory distress, or feeding difficulty. In infancy, they can be biologically benign, even when their histologic characteristics are immature. Surgery is the treatment of choice for all three masses and may be curative.