[Unusual CT and MRI appearance of the epidermoid tumor--a case report].

We reported a case of epidermoid tumor with unusual findings on CT and MRI. A 41-year old woman was admitted because of headache. On admission she had no neurological deficits. CT revealed a lobular homogenous high-dense mass with a sharp margin in the mid-portion of the posterior fossa. The mass was shown as a low signal intensity on both T1- and T2-weighted MRI. An encapsulated mass containing "motor oil" like viscid fluid was removed by surgical operation. Histological examination revealed epidermoid cyst. CT-dense epidermoid tumor was discussed with referring to the literature.