A benign, slow-growing lesion of the skull due to aberrant epidermal inclusion in the calvaria. Differential diagnosis is Langerhans cell histiocytosis in a child/young adult, metastasis and plasmacytoma. Key to diagnosis is the intradiploic location with well-demarcated lysis expanding both the inner and outer tables of the skull and well defined borders. The MRI findings of marked restricted diffusion are typical of epidermoid.