Bilateral lambdoid dermoid cyst.

Generally, dermoid and epidermoid cysts arise as a result of incomplete separation of the neuroectoderm from the superficial ectoderm with displacement of ectodermal elements along their lines of fusion during development. Dermoid cysts of the posterior head are rare lesions composed of epidermal and mesodermal elements. Furthermore, dermoid cysts in the occipital area are extremely rare. The presence of synchronous, bilateral occipital dermoids is quite rare and has not been reported previously. A unique case of lambdoidal dermoids in a 75-year-old woman is presented. Large right lesion was excised concurrently through direct skin incision, and a very small left mass was observed. And the etiology, natural history, management, and prognosis of dermoids are reviewed.