Epidermoid tumor represent 0.2%-1% of all primary intracranial neoplasms.
Both congenital and acquired epidermoid cyst occur. Congenital epidermoid is nonneoplastic inclusion cyst.Aquired epidermoid cyst developed as a result of trauma.
Pathology
Gross pathology Intracranial epidermoid tumors are well delineated cystic lesions. They have an irregular lobulated ,or cauliflower-like outer surface has shiny mother of pearl appearance. The cyst is filled with soft, waxy of flaky keratohyalin.

No dermal appendages

Epidermoid tumors occur between 20 to 60 yrs.  There is no gender predilection.

Location is off midline 40% to 50% in cerebellopontine angle cistern,10% to 15% parasellar and middle fossa space,10% diploic spaces.
RADIOLOGY

CT-  NECT shows low density, calcification is uncommon
CECT shows occasional peripheral enhancement.

MR-  Signal characteristic onT1WI and T2WI similar to CSF and heterogenous on FLAIR sequence.
Diffusion weighted MR useful in distinguishing arachnoid cyst and epidermoid.The ADC of arachnoid cyst is similar to stationary water,ADC   of epidermoid is similar to brain parenchyma