Large Intradiploic Epidermoid Cyst of the Temporal Bone

Intradiploic epidermoid cyst of the skull, despite being rare and representing less than 1% of all intracranial tumors, is a benign lesion that is derived from an ectodermal cell rest within the cranium. The frontal and parietal bones are the most common sites for the cyst; however, the temporal bone, although rarely, is also involved. Intradiploic epidermoid cysts have slow growth rates and often grow to enormous sizes without producing any measurable neurological symptoms. For treatment, a complete removal of the cyst with its capsule is important to avoid recurrence. Very rare malignant transformations of the cysts have been reported, generally in cases with repeated recurrences or infections. A 16-year-old female patient was diagnosed with a temporal bone intradiploic epidermoid cyst behind the left mastoid cavity, which was successfully removed through a transmastoid approach.