Sections show a cyst wall lining with a thin layer of stratified squamous epithelium including a granular cell layer, with bland nuclear features and surface keratinisation. There is abundant Iamellated keratin debris. The wall is fibrous with areas of infiltration by mononuclear chronic inflammatory cells, foreign body type multinucleate giant cells, in association with cholesterol clefts. The inflammatory process focally extends into bone. There is no brain tissue identified. There are no adnexal skin structures or immature elements. There is no evidence of malignancy.
FINAL DIAGNOSIS: epidermoid cyst.