Giant epidermal inclusion cyst of buttock.

Epidermal inclusion cyst is a common benign soft-tissue lesion of skin. It often presents as a small lesion, but rarely grows to a large mass. We are presenting a giant gluteal epidermal inclusion cyst that grew to an enormous size, masquerading as a large soft-tissue neoplasm. Magnetic resonance imaging not only displays the size and margins of these well-encapsulated lesions in three planes, but shows characteristic internal features that may suggest the preoperative diagnosis.