Section Editor: Sandy Cheng-Yu Chen, M.D.
Taipei Medical University Hospital, Taipei, Taiwan
Epidermal inclusion cysts (EIC), also called epidermoid (inclusion) cysts, are benign and often incidentally found lesions of the scalp and skull at fontanel. Usually, these lesions do not require treatment but in case of infection or continued growth, incision and drainage or surgical excision may be necessary. Scalp EIC typically demonstrate T1 low to intermediate signal intensity (A, arrow) and hyperintense on T2-weighted sequences (B, arrow). Enhancement of EIC on post-contrast MR images is variable but when present, it is classically peripheral (C and D, arrows). An intraosseous EIC often does not show diffusion restriction as opposed to the intracranial ones.