Giant Intradiploic Epidermoid Cyst of the Skull: A Case Report and Management of Large Cystic Scalp Masses

Epidermoid cysts of the skull are very rare, benign, slow-growing tumors. Only a very few cases have ever been reported and they can be found in the diploë, the cranial cavity, or in the spinal canal. Intradiploic epidermoid cysts are even rarer and can be found in any part of the skull. There are 2 theories regard-ing the derivation of these cysts. One theory suggests that they are derived from ectodermal tissue misplaced in the cranial bones during embryonic development. The alternate theory suggests possible traumatic implantation of these cells. They often reach a large size (3–5 cm) without creating neurologic symptoms. A 34-year-old man was seen for resection of a large melanoma on his right arm, and in the workup he was noted to have a large, long-standing lesion on the posterior scalp. After radiologic assess-ment was completed, the right parietooccipital lesion was removed with a subsequent cranioplasty. The management of this lesion was handled appropriately but could have led to disastrous consequences if a more cavalier approach had been taken. The clinical presentation, pathologic findings, radiologic features, and treatment of the lesion are reviewed.