The patient went on to have a resection.

Histology

MICROSCOPIC DESCRIPTION: The section shows a collapsed cyst. This is lined by squamous epithelium with a discernible granular layer. The contents comprise laminated keratin. No appendageal structures are identified. The features are of an epidermal cyst. No evidence of tumor is seen. The specimen includes fragments of viable lamellar bone.

FINAL DIAGNOSIS: Epidermoid cyst

Discussion

These are typical findings of an epidermoid cyst, a potentially tricky diagnosis if DWI not available.