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[0] Dermoid cyst [1] Uncommon [2] Inclusion of ectodermal elements during closure of neural groove between the third and fifth weeks of embryonic life. Malformation of the adjacent structure can occur. Some of them may remain communicating with the overlying skin through a dermal sinus. Traumatic introduction of skin fragment is also a possible mechanism. [3] Most of them are intracranial and arise in the posterior fossa, usually along the midline in the vermis. About one-tenth of all cases are intraspinal and they are most commonly found in the lumbosacral region; they can be both intra- or extramedullary. [4] Most of the spinal cases are discovered in the first and second decades of life; intracranial cases are seen in slightly older patients. Symptoms are usually due to local compression, irritation and to increased intracranial pressure due to hydrocephalus. Leakage of the kertinous content will lead to extensive granulomatous meningitis. [6] The internal lining is very similar to skin and skin appendages are present. Leakage or escape of the content may lead to a wide spread granulomatous meningitis with foreign body giant cell reaction. [5] 
Well-defined round to oval, opaque, "pearly" mass of variable size. The thickness of the wall is variable. The content is greasy material due to secretion of sebaceous glands. A variable amount of hair is present. Solid components may be present. The distinction between dermoid cyst and cystic teratoma is not entirely sharp.
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